[MM-19711] - Get plugin configuration without removing secrets (#11928)

* Method GetUnsanitizedConfig() exposed to API (Plugin) interface and his implementations

* improvements with some suggestions

* Fix documentation (final period added)

Co-Authored-By: Ali Farooq <25732808+ali-farooq0@users.noreply.github.com>

* Added some test for Plugin.GetConfig and Plugin.GetUnsanitizedConfig

* Removed empty lines

plugin/api.go

@@ -31,6 +31,11 @@ type API interface {
 	// GetConfig fetches the currently persisted config
 	GetConfig() *model.Config
 
+	// GetUnsanitizedConfig fetches the currently persisted config without removing secrets.
+	//
+	// Minimum server version: 5.16
+	GetUnsanitizedConfig() *model.Config
+
 	// SaveConfig sets the given config and persists the changes
 	SaveConfig(config *model.Config) *model.AppError