feat(AppConfig): iterate how apps are managed

- auth clients are always shared, cannot be disabled
- custom connections are enabled by default, can be disabled
- any existing connections can be reconnected regardless of its AppConfig or AppAuthClient states

packages/backend/test/mocks/rest/api/v1/apps/get-connections.js

@@ -3,7 +3,6 @@ const getConnectionsMock = (connections) => {
     data: connections.map((connection) => ({
       id: connection.id,
       key: connection.key,
-      reconnectable: connection.reconnectable,
       verified: connection.verified,
       appAuthClientId: connection.appAuthClientId,
       formattedData: {