Add dynamic client registration

[DeepDiver1975]

Description

This adds dynamic client registration to phoenix according to https://openid.net/specs/openid-connect-registration-1_0.html

Related Issue

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How Has This Been Tested?

    "openIdConnect": {
      "authority": "https://ocis-bridge.owncloud.works",
      "scope": "openid profile email offline_access",
      "dynamic": true
    },

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)
• Technical debt
• Tests

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

Open tasks:

• ...

[LukasHirt]

LGTM 👍