Group flags by type

[brmzkw]

We use cobra to parse arguments, which unfortunately does not allow to group flags together (see this issue).

The output of commands such as koyeb service create --help or koyeb service update --help could be improved. Instead of having all the flags sorted alphabetically:

Flags:
  -a, --app string                              Service application
      --checks strings                          Update service healthchecks (available for services of type "web" only)
                                                For HTTP healthchecks, use the format <PORT>:http:<PATH>, for example --checks 8080:http:/health
                                                For TCP healthchecks, use the format <PORT>:tcp, for example --checks 8080:tcp
                                                To delete a healthcheck, use !PORT, for example --checks '!8080'
      --docker string                           Docker image
      --docker-args strings                     Docker args
      --docker-command string                   Docker command
      --docker-entrypoint strings               Docker entrypoint
      --docker-private-registry-secret string   Docker private registry secret
      --env strings                             Update service environment variables using the format KEY=VALUE, for example --env FOO=bar
                                                To use the value of a secret as an environment variable, specify the secret name preceded by @, for example --env FOO=@bar
                                                To delete an environment variable, prefix its name with '!', for example --env '!FOO'
      --git string                              Git repository
      --git-branch string                       Git branch
      --git-build-command string                Buid command (legacy, prefer git-buildpack-build-command)
      --git-builder string                      Builder to use, either "buildpack" (default) or "docker" (default "buildpack")
      --git-buildpack-build-command string      Buid command
      --git-buildpack-run-command string        Run command
      --git-docker-args strings                 Arguments for the Docker CMD
      --git-docker-command string               Docker CMD
      --git-docker-dockerfile string            Dockerfile path
      --git-docker-entrypoint strings           Docker entrypoint
      --git-docker-target string                Docker target
      --git-no-deploy-on-push                   Disable new deployments creation when code changes are pushed on the configured branch
      --git-run-command string                  Run command (legacy, prefer git-buildpack-run-command)
      --git-workdir string                      Path to the sub-directory containing the code to build and deploy
  -h, --help                                    help for create
      --instance-type string                    Instance type (default "nano")
      --max-scale int                           Max scale (default 1)
      --min-scale int                           Min scale (default 1)
      --ports strings                           Update service ports (available for services of type "web" only) using the format PORT[:PROTOCOL], for example --port 80:http
                                                If no protocol is specified, it defaults to "http". Supported protocols are "http" and "http2"
                                                To delete an exposed port, prefix its number with '!', for example --port '!80'

      --regions strings                         Regions (default [fra])
      --routes strings                          Update service routes (available for services of type "web" only) using the format PATH[:PORT], for example '/foo:8080'
                                                If no port is specified, it defaults to 80
                                                To delete a route, use '!PATH', for example --route '!/foo'

      --type string                             Service type, either "web" or "worker" (default "web")

we could group the flags by type (source type, builder type), and have a description for each type, for example:

General flags:
  -a, --app string                              Service application
      --env strings                             Update service environment variables using the format KEY=VALUE, for example --env FOO=bar
                                                To use the value of a secret as an environment variable, specify the secret name preceded by @, for example --env FOO=@bar
                                                To delete an environment variable, prefix its name with '!', for example --env '!FOO'
  -h, --help                                    help for create
      --instance-type string                    Instance type (default "nano")
      --max-scale int                           Max scale (default 1)
      --min-scale int                           Min scale (default 1)
      --regions strings                         Regions (default [fra])
      --type string                             Service type, either "web" or "worker" (default "web")

Web services: the flags below can only be set for services with --type=web
      --checks strings                          Update service healthchecks (available for services of type "web" only)
                                                For HTTP healthchecks, use the format <PORT>:http:<PATH>, for example --checks 8080:http:/health
                                                For TCP healthchecks, use the format <PORT>:tcp, for example --checks 8080:tcp
                                                To delete a healthcheck, use !PORT, for example --checks '!8080'
      --ports strings                           Update service ports (available for services of type "web" only) using the format PORT[:PROTOCOL], for example --port 80:http
                                                If no protocol is specified, it defaults to "http". Supported protocols are "http" and "http2"
                                                To delete an exposed port, prefix its number with '!', for example --port '!80'
      --routes strings                          Update service routes (available for services of type "web" only) using the format PATH[:PORT], for example '/foo:8080'
                                                If no port is specified, it defaults to 80
                                                To delete a route, use '!PATH', for example --route '!/foo'
												
Flags to deploy a docker container:
      --docker string                           Docker image
      --docker-args strings                     Docker args
      --docker-command string                   Docker command
      --docker-entrypoint strings               Docker entrypoint
      --docker-private-registry-secret string   Docker private registry secret

Flags to deploy a GitHub repository:
      --git string                              Git repository
      --git-branch string                       Git branch
      --git-builder string                      Builder to use, either "buildpack" (default) or "docker" (default "buildpack")
      --git-no-deploy-on-push                   Disable new deployments creation when code changes are pushed on the configured branch
      --git-workdir string                      Path to the sub-directory containing the code to build and deplo

Flags to build a GitHub repository with the buildpack builder:
      --git-buildpack-build-command string      Buid command
      --git-build-command string                Buid command (legacy, prefer git-buildpack-build-command
      --git-buildpack-run-command string        Run command
      --git-run-command string                  Run command (legacy, prefer git-buildpack-run-command

Flags to build a GitHub repository with the Docker builder:
      --git-docker-args strings                 Arguments for the Docker CMD
      --git-docker-command string               Docker CMD
      --git-docker-dockerfile string            Dockerfile path
      --git-docker-entrypoint strings           Docker entrypoint
      --git-docker-target string                Docker target

I don't know how to do the grouping. Maybe could we check this PR, or check how Karmada did