:sparkles: [ENH] Allow the user to make generic search request

[CChemin]

We need a search endpoint with a non fixed number of paramaters you can search on. For example we might want to filter by values in the properties map without having to add in the endpoint each possibilities.
A format we might adopt can be something like /realms/users?request=attributes.insee_roles_applicatifs&mail=mymail@insee.fr . Maybe there are standards for search we can look at.
The already existing StoreMapping model should be of help to resolve this issue.