Implement endpoints required by the Contribution Interface MVP

As the (Advanced) Contribution Interface project moving forward will need the following [MVP features](https://github.com/dis-moi/contribution-Interface/issues?q=is%3Aissue+is%3Aopen+label%3AMVP)

Are the following endpoints implemented yet @Goutte
- If so let's tick the boxed and the name exact name instead.
- if not, we will implement the missing endpoints in this issue

Features:
- [ ] create a deactivated user (signup) (https://github.com/dis-moi/contribution-Interface/issues/1)
- [ ] activate a user given the right token (once its email is validated) (https://github.com/dis-moi/contribution-Interface/issues/1)
- [ ] create a contributor for my user (https://github.com/dis-moi/contribution-Interface/issues/3)
- [ ] request a new password for a user (when a user lost his) (see https://github.com/dis-moi/contribution-Interface/issues/6)
- [ ] logout - invalidate user token (https://github.com/dis-moi/contribution-Interface/issues/5)
- [ ] login - given i am an activated user - (https://github.com/dis-moi/contribution-Interface/issues/2)
- [ ] Publish a notice under my "contributor account" (https://github.com/dis-moi/contribution-Interface/issues/4)
- [ ] Retrieve the list of my notices (filter notices by contributor) (https://github.com/dis-moi/contribution-Interface/issues/14)
- [ ] Retrieve the number of subscribers of a contributor (https://github.com/dis-moi/contribution-Interface/issues/14)

Start by reviewing the linked MVP issues and checking which of the listed endpoints already exist in the backend. Done means the missing signup, activation, contributor, password, logout, login, notice, notice-list, and subscriber-count endpoints are implemented and the checklist can be updated.

Written by the indexing model from the issue text.