Allow administrator to manage API Key

[RignonNoel]

Expected behavior

• Administrators can generate API KEYS to allow them to script some actions with Volontaria (ex.: creating all the Events for next year from a XSLX file they maintain in intern)

Current behavior

• User can use the API of Volontaria directly but they can't create new API Key to separate their usage and secure their permissions
• If user logout and login he needs to change his API KEY everywhere

Potential solution

• Create a new model ApplicationKey who contain:
  • A CharField name to help administrators manage their API KEYS
  • A CharField key that is auto-generated on creation
  • A DatetimeField created_at to help administrators manage their API KEYS
  • A DatetimeField last_used_at to help administrators manage their API KEYS
• Overwrite authentication system to allow usage of the API KEYS
• Each time the API KEYS is used, update the API KEY last usage

[Vardane]

Starting work on this issue as discussed.