Migrate management of OAuth applications to CRUD list

• No inline editing
• Will need file upload → exclude the icon field for now, the fix for this is coming in !1594
• Right now, it is shown as an ugly list, just use the CRUD table
• Client ID and client secret are generated server side and have to be shown one time before the secret gets hashed → get values via separate GraphQL query and prefill them read-only, then just send them as regular values in the mutation