Add allowOverride app source option

lib/app_sources/coolapk.dart

@@ -13,6 +13,7 @@ class CoolApk extends AppSource {
     hosts = ['www.coolapk.com', 'api2.coolapk.com'];
     allowSubDomains = true;
     naiveStandardVersionDetection = true;
+    allowOverride = false;
   }
 
   @override

lib/pages/add_app.dart

@@ -407,8 +407,14 @@ class AddAppPageState extends State<AddAppPage> {
                         defaultValue: pickedSourceOverride ?? '',
                         [
                           MapEntry('', tr('none')),
-                          ...sourceProvider.sources.map(
-                              (s) => MapEntry(s.runtimeType.toString(), s.name))
+                          ...sourceProvider.sources
+                              .where((s) =>
+                                  s.allowOverride ||
+                                  (pickedSource != null &&
+                                      pickedSource.runtimeType ==
+                                          s.runtimeType))
+                              .map((s) =>
+                                  MapEntry(s.runtimeType.toString(), s.name))
                         ],
                         label: tr('overrideSource'))
                   ]

lib/providers/source_provider.dart

@@ -586,6 +586,7 @@ abstract class AppSource {
   bool appIdInferIsOptional = false;
   bool allowSubDomains = false;
   bool naiveStandardVersionDetection = false;
+  bool allowOverride = true;
   bool neverAutoSelect = false;
   bool showReleaseDateAsVersionToggle = false;
   bool versionDetectionDisallowed = false;