dag: Support step continueOn based on command output and exitcode

[yohamta]

Background

Currently, the continueOn configuration for DAG steps only supports static conditions like exit codes. There's a need to make this more dynamic by allowing continuation decisions based on the actual command output.

Proposed Feature

Add support for output-based conditions in the continueOn configuration. This would allow steps to continue execution even after a failure if the command output matches specified patterns.

steps:
  # 1. Continue on based on exit code
  - name: step 1
    command: echo hello
    continueOn:
      exitCode: [0,1] # continue on if the exitcode is one of these
      
  # 2. Continue on based on stderr / stdout
  - name: step 2
    command: echo hello
    continueOn: # continue of if the stdout/stderr contains the following outputs
      stderr: "hello"
      stdout: "bye"
        
  # 3. Continue on based on environment variable / command substitution
  - name: step 3
    command: echo hello
    output: FOO
    continueOn:
      condition: "$FOO" # This can be a command substitution such as: condition: "`echo $FOO`".
      expected: # continue on if $FOO contains one of the expected texts
        - "hello"
        - "bye"
 
  # 4. Continue on based on the output value
  - name: step 4
    command: echo hello
    output: FOO
    continueOn:
      output: # continue on if $FOO contains one of the expected texts
        - "hello"
        - "bye"