settings: add setting FARGO_MAX_DOCUMENTS_PER_USER (#41491)

Limit on number of documents uploaded by an user and stored for him,
it does not apply to documents with an origin (usually uploaded through
the REST API).

fargo/settings.py

@@ -174,6 +174,8 @@ FARGO_MAX_DOCUMENT_SIZE = 4 * 1024 * 1024  # 4 Mo
 
 FARGO_MAX_DOCUMENT_BOX_SIZE = 20 * 1024 * 1024  # 20 Mo
 
+FARGO_MAX_DOCUMENTS_PER_USER = 100
+
 FARGO_VALIDATION_LIFETIME = 3600 * 24 * 31 * 6  # nearly 6 months
 
 FARGO_DOCUMENT_TYPES = [