[core] Rework Profile Edge Function (#34)

This commit introduces a new "profile-v2" edge function and deprecates
the "profile-v1" edge function. We decided to provide a new edge
function for all profile related operation to improve the handling of
the different operation the edge function is responsible for.

The main differences to the "profile-v1" functions are:
- Pass the operation id within the request url instead of the body of
  the request.
- Move the operations for accounts (e.g. GitHub) to seperate files, to
  improve the readability of the function.
- Do not require the "sourceType" anymore, instead we are using the
  operation id and request method to determine the operation which
  should be executed
- The request body is now only used for the data of the corresponding
  account and not for any other information like the operation id and
  source information.

app/lib/widgets/settings/accounts/settings_accounts_github.dart

@@ -35,7 +35,7 @@ class SettingsAccountsGithub extends StatelessWidget {
       await Provider.of<ProfileRepository>(
         context,
         listen: false,
-      ).deleteGithubAccount();
+      ).githubDeleteAccount();
     } catch (_) {}
   }
 
@@ -166,7 +166,7 @@ class _SettingsAccountsGithubAddState extends State<SettingsAccountsGithubAdd> {
         await Provider.of<ProfileRepository>(
           context,
           listen: false,
-        ).addGithubAccount(_tokenController.text);
+        ).githubAddAccount(_tokenController.text);
 
         setState(() {
           _isLoading = false;