Add SCIM support

[coudot]

The goal would be to use Service Desk as a SCIM server to be able to manage LDAP entries through SCIM

It could benefit from SD features lik hooks and audit

[davidcoutadeur]

Coding this feature could be easier if we first design APIs for all CRUD functions.

Currently, we have only one API for searching entries, it would be nice to have those for create/update/rename/delete entries.

Then, we could develop the interfaces on the top of these APIs, among which a SCIM interface.