feat: add plugin config

Author: saitho

README.md

@@ -0,0 +1,35 @@
+# StackHead Plugin API
+
+## Expected structure
+
+```go
+package main
+
+import "github.com/getstackhead/pluginlib"
+
+type MyPlugin struct {
+}
+
+func (p MyPlugin) Setup() {
+	// implement software setup action
+}
+
+func (p MyPlugin) Deploy(project pluginlib.Project) {
+	// implement project deploy action
+}
+
+func (p MyPlugin) Destroy(project pluginlib.Project) {
+	// implement project destroy action
+}
+
+func (p MyPlugin) HookPreTerraformPlan(project pluginlib.Project) {
+	// pre terraform plan hook (to be implemented)
+}
+
+// Export plugin to StackHead. Must be named "Plugin"!
+var Plugin MyPlugin
+```
+
+```shell
+go build -buildmode=plugin -o plugin_myplugin.so main.go
+```

plugin.go

@@ -1,6 +1,34 @@
 package pluginlib
 
+import (
+	"plugin"
+)
+
 type Plugin interface {
-	Deploy(project Project)
+	GetConfig() PluginConfig
 	Setup()
+	Deploy(project Project)
+	Destroy(project Project)
+}
+
+func LoadPlugin(path string) (Plugin, error) {
+	// load module
+	plug, err := plugin.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	// 2. look up a symbol (an exported function or variable)
+	symPlugin, err := plug.Lookup("Plugin")
+	if err != nil {
+		return nil, err
+	}
+
+	// 3. Assert that loaded symbol is of a desired type
+	var plugin Plugin
+	plugin, ok := symPlugin.(Plugin)
+	if !ok {
+		return nil, err
+	}
+	return plugin, nil
 }

plugin_config.go

@@ -0,0 +1,31 @@
+package pluginlib
+
+var PluginType = struct {
+	PROXY     int
+	CONTAINER int
+	DNS       int
+	MISC      int
+}{
+	PROXY:     0,
+	CONTAINER: 1,
+	DNS:       2,
+	MISC:      3,
+}
+
+type TerraformProvider struct {
+	name               string
+	vendor             string
+	version            string
+	resourceName       string
+	init               string
+	providerPerProject bool
+}
+
+type PluginConfig struct {
+	Name        string
+	Description string
+	Version     string
+	Author      string
+	PluginType  int
+	Terraform   TerraformProvider
+}