feat(collaboration): Set IsAdminUser property for Collabora

This set the 'IsAdminUser' Property correctly in the CheckFileInfo
Response. For that a new Permission 'WebOffice.Manage' is introduced. By
default this permission is only assigned to the Admin role.
User with this permission get access to certain admin features in
Collabora (e.g. the 'Server Audit' dashboard)

Closes: #796
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f