Prepare 8.4.0

[julien-nc]

Added

• feat(upsert): new options to read client secret from env var or file @julien-nc #1324
• Add documentation for the different types of group claims @s3n-w6i #1339

Changed

• Refactoring @solracsf #1319 #1320 #1321 #1322

Fixed

• Handle string Content-Type headers during avatar provisioning @mod242 #1302
• fix(discovery): do not cache the discovery response if it can't be decoded @julien-nc #1304
• fix(jwks): filter unsupported key types to prevent Firebase JWT crash @strobelpierre #1333
• canonicalize locale string @alejo7797 #1336
• fix(id4me): use mozart to move id4me/id4me-rp in lib/Vendor and adjust its namespace so it is not imported by other files in Nextcloud @julien-nc #1337
• fix(ldap-service): in LdapService::isLdapDeletedUser, make an early return to false if the user_ldap app is NOT enabled @julien-nc #1340