feat: add a post-registry-login trigger

This allows other plugins to execute commands after a registry has been authenticated against.

docs/development/plugin-triggers.md

@@ -1757,6 +1757,20 @@ APP="$1"
 haproxy-build-config "$APP"
 ```
 
+### `post-registry-login`
+
+- Description: Allows running a command after the a registry has been logged into
+- Invoked by: `dokku registry:login`
+- Arguments: `$DOCKER_REGISTRY_SERVER $DOCKER_REGISTRY_USER`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+# the DOCKER_REGISTRY_PASS env var is also set
+echo "$DOCKER_REGISTRY_PASS"
+```
+
 ### `post-release-builder`
 
 > [!WARNING]

plugins/common/plugn.go

@@ -16,6 +16,7 @@ import (
 type PlugnTriggerInput struct {
 	Args          []string
 	CaptureOutput bool
+	Env           map[string]string
 	StreamStdio   bool
 	Trigger       string
 }
@@ -42,6 +43,11 @@ func CallPlugnTrigger(input PlugnTriggerInput) (execute.ExecResult, error) {
 	if isatty && !input.CaptureOutput {
 		env = append(env, "FORCE_TTY=1")
 	}
+	if input.Env != nil {
+		for k, v := range input.Env {
+			env = append(env, fmt.Sprintf("%s=%s", k, v))
+		}
+	}
 
 	args := []string{"trigger", input.Trigger}
 	args = append(args, input.Args...)

plugins/registry/subcommands.go

@@ -53,6 +53,19 @@ func CommandLogin(server string, username string, password string, passwordStdin
 		return errors.New("Failed to log into registry")
 	}
 
+	_, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
+		Trigger:       "post-registry-login",
+		Args:          []string{server, username},
+		StreamStdio:   true,
+		CaptureOutput: false,
+		Env: map[string]string{
+			"DOCKER_REGISTRY_PASS": password,
+		},
+	})
+	if err != nil {
+		return err
+	}
+
 	return nil
 }