Add custom OIDC scope

[gpongelli]

Description

This PR add the iOS side to manage OIDC custom scopes, as it can be already done with WEB_OIDC_SCOPE .
its companion PR on sdk side is opencloud-eu/ios-sdk#4 .

Related Issue

#27

Motivation and Context

When managing custom roles through LLDAP and Authelia, OpenCloud does not work correctly due to fixed OIDC scopes, see discussion linked in related issue #27 like this, this or this or this discussion I made .

A solution could be to add a custom scopes field into iOS app, and accept it server-side as same as it was done for WEB_OIDC_SCOPE (server side part is still missing, see error below).

How Has This Been Tested?

Manually.

Actually the code ends with error due to server side that does not accept extra scopes:

2025-12-26 16:49:54.318000+0100 OpenCloud[8307.114983] ⚪️ | [AUTH, Openid-Connect] Auth session returned with callbackURL=oc://ios.opencloud.eu?error=invalid_scope&error_description=The+requested+scope+is+invalid%2C+unknown%2C+or+malformed.+The+OAuth+2.0+Client+is+not+allowed+to+request+scope+%27banana%27.&iss=https%3A%2F%2F<authelia-path>&state=401D8657-0D20-438C-9DB2-A01C7A027E77, error=(null) [OCAuthenticationMethodOAuth2.m:451|FULL]

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• Added an issue with details about all relevant changes in the docs repository.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have set a pull request label and a meaningful title for changelog automation
• related PR into ios-sdk Feature/custom OIDC scope ios-sdk#4