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/apps/apps.go

@@ -5,11 +5,13 @@ var (
 	DefaultProperties = map[string]string{
 		"deploy-source":          "",
 		"deploy-source-metadata": "",
+		"disable-autocreation":   "",
 	}
 
 	// GlobalProperties is a map of all valid global apps properties
 	GlobalProperties = map[string]bool{
 		"deploy-source":          true,
 		"deploy-source-metadata": true,
+		"disable-autocreation":   true,
 	}
 )

plugins/apps/functions.go

@@ -132,11 +132,7 @@ func maybeCreateApp(appName string) error {
 		return nil
 	}
 
-	results, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
-		Trigger: "config-get-global",
-		Args:    []string{"DOKKU_DISABLE_APP_AUTOCREATION"},
-	})
-	disableAutocreate := results.StdoutContents()
+	disableAutocreate := common.PropertyGetDefault("apps", "--global", "disable-autocreation", "")
 	if disableAutocreate == "true" {
 		common.LogWarn("App auto-creation disabled.")
 		return fmt.Errorf("Re-enable app auto-creation or create an app with 'dokku apps:create %s'", appName)

plugins/apps/triggers.go

@@ -53,6 +53,15 @@ func TriggerInstall() error {
 		return nil
 	}
 
+	if err := common.MigrateConfigToProperties("apps", []common.MigrateConfigEntry{
+		{
+			GlobalConfigVar: "DOKKU_DISABLE_APP_AUTOCREATION",
+			Property:        "disable-autocreation",
+		},
+	}); err != nil {
+		return err
+	}
+
 	// migrate all created-at values from app mod-time to property
 	for _, appName := range apps {
 		if common.PropertyExists("apps", appName, "created-at") {