[MM-40735] Add MattermostAppID to OAuth app (#19214)

store/storetest/oauth_store.go

@@ -48,9 +48,14 @@ func testOAuthStoreSaveApp(t *testing.T, ss store.Store) {
 	_, err = ss.OAuth().SaveApp(&a1)
 	require.Error(t, err, "Should have failed, app should be invalid cause it doesn' have a name set")
 
+	a1.Name = "TestApp" + model.NewId() // Valid name
+	a1.MattermostAppID = "a very, very, very, very, very, very, very long id"
+	_, err = ss.OAuth().SaveApp(&a1)
+	require.Error(t, err, "Should have failed, app should be invalid cause the MattermostAppID is to long")
+
 	// Save the app
 	a1.Id = ""
-	a1.Name = "TestApp" + model.NewId()
+	a1.MattermostAppID = "some small id" // Valid id
 	_, err = ss.OAuth().SaveApp(&a1)
 	require.NoError(t, err)
 }