GitLab

* Add get_source_value to utils, and use it to get value from object or dict

* GitHub connector

* fix codacy

* remove print statement

* Remove Github Connector

* Data Migration Connector

- Create new connection with boilerplate
- Add Run button in Data Migration Plan

* minor

* fix codacy

* remove pygithub

* Minor

- Remove button from form and add to custom button
- Remove is_custom field
- Add Connector Type 'Custom'
- Show New Connection button only in developer mode

* [fix] logging

- only store the name, not the whole json

* [fix] tests