feat: migrate environment variables to plugin properties

Standardize how environment variables are migrated to properties during
install triggers and migrate all remaining DOKKU_* config vars to their
appropriate plugin properties.

Adds a reusable MigrateConfigToProperties() function in the common
package with Transform callback and ListProperty support, plus a
migrate-config-to-property subcommand for the prop binary so shell
plugins can use the same code path.

Migrated variables and their new property owners:
- DOKKU_APP_PROXY_TYPE/DOKKU_PROXY_TYPE → proxy type
- DOKKU_DISABLE_PROXY → proxy disabled
- DOKKU_PROXY_PORT → ports proxy-port
- DOKKU_PROXY_SSL_PORT → ports proxy-ssl-port
- DOKKU_APP_RESTORE → ps restore
- DOKKU_SKIP_DEPLOY → ps skip-deploy
- DOKKU_START_CMD → ps start-cmd
- DOKKU_DOCKERFILE_START_CMD → ps dockerfile-start-cmd
- DOKKU_DISABLE_APP_AUTOCREATION → apps disable-autocreation
- DOKKU_APP_SHELL → scheduler shell
- DOKKU_SKIP_CLEANUP → builder skip-cleanup
- DOKKU_CHECKS_DISABLED → checks disabled
- DOKKU_CHECKS_SKIPPED → checks skipped
- DOKKU_CHECKS_WAIT → checks wait
- DOKKU_CHECKS_TIMEOUT → checks timeout
- DOKKU_CHECKS_ATTEMPTS → checks attempts
- DOKKU_DEFAULT_CHECKS_WAIT → checks default-wait
- DOKKU_SKIP_ALL_CHECKS → checks disabled (legacy)
- DOKKU_SKIP_DEFAULT_CHECKS → checks skipped (legacy)

Also refactors existing bespoke migration loops in scheduler, ports, ps,
builder, and nginx-vhosts plugins to use the standardized utility.

Removes DOKKU_PARALLEL_ARGUMENTS from documentation (unused in core).
Deprecates fn-migrate-config-to-property bash function.

closes #1558

plugins/builder/builder.go

@@ -3,14 +3,16 @@ package builder
 var (
 	// DefaultProperties is a map of all valid builder properties with corresponding default property values
 	DefaultProperties = map[string]string{
-		"selected":  "",
-		"detected":  "",
-		"build-dir": "",
+		"build-dir":    "",
+		"detected":     "",
+		"selected":     "",
+		"skip-cleanup": "",
 	}
 
 	// GlobalProperties is a map of all valid global builder properties
 	GlobalProperties = map[string]bool{
-		"selected":  true,
-		"build-dir": true,
+		"build-dir":    true,
+		"selected":     true,
+		"skip-cleanup": true,
 	}
 )

plugins/builder/triggers.go

@@ -108,30 +108,21 @@ func TriggerInstall() error {
 		return fmt.Errorf("Unable to install the builder plugin: %s", err.Error())
 	}
 
-	apps, err := common.UnfilteredDokkuApps()
-	if err != nil && !errors.Is(err, common.NoAppsExist) {
-		return nil
+	if err := common.MigrateConfigToProperties("builder", []common.MigrateConfigEntry{
+		{
+			ConfigVar: "DOKKU_APP_TYPE",
+			Property:  "detected",
+		},
+		{
+			ConfigVar:       "DOKKU_SKIP_CLEANUP",
+			GlobalConfigVar: "DOKKU_SKIP_CLEANUP",
+			Property:        "skip-cleanup",
+		},
+	}); err != nil {
+		return err
 	}
 
-	for _, appName := range apps {
-		if common.PropertyExists("builder", appName, "detected") {
-			continue
-		}
-
-		results, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
-			Trigger: "config-get",
-			Args:    []string{appName, "DOKKU_APP_TYPE"},
-		})
-		if err != nil {
-			return err
-		}
-
-		if results.StdoutContents() != "" {
-			common.PropertyWrite("builder", appName, "detected", results.StdoutContents())
-		}
-	}
-
-	_, err = common.CallPlugnTrigger(common.PlugnTriggerInput{
+	_, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
 		Trigger: "install-builder-prune",
 	})