Check if user already has avatar

[wecodemore]

Check if user already has avatar

[kraftner]

@franz-josef-kaiser and me seem to agree that option 3, "outright refuse to upload the second avatar" is the way to go.

[franz-josef-kaiser]

As discussed in @kraftner office yesterday:

• Outright deleting an attachment if another one is present is unexpected behavior. To make this a viable option, the plugin also would need to prompt the user if they really want to do this and possibly offer an "undo" step. This would make the process much more complicated as the attachment post would need to go into trash, which then depends on the config settings and it might not be clear to the user that setting zero trash days or deactivating revisions will not allow an "undo" step. The chance that the user will learn this by "try, fail, blame plugin author, never read docs" is high and too risky. Also there would need to be additional UI elements, etc. making the code even more complex with little to gain.
• Remove the link between avatar attachment and user from both ends: Currently the connection via IDs gets disconnected on only one end. @kraftner please clarify: the connection "attachment⇒user" stays, but the user only has a single meta entry, correct? If so, then this actually is expected behavior and correct. I remember that I did this to make history of previous avatars/ logos possible. Maybe I just thought about – I am not completely sure. We might want to consider leaving it "as is", but make this behavior consistent and optional. Read: add a filter to not delete attachments, add a ticket to allow the user to browse their history of previous avatars, like Gravatar allows to decide which avatar you want to use for which email-account. This should then go into a second issue.
• Outright refuse to upload the second avatar: This is what we decided now and the focus of this issue should stay with this. It is unexpected if you upload two avatars that you see your old one in one tab, then reload and get presented a new one. Forcing the user to actively click the "trashbin"-icon in the upper right makes usage more clear. We might consider using the Pointers API to tell the user where they have to click. WP.SE answer from @Giuseppe-Mazzapica on this topic.

[kraftner]

Concerning the second point:

the connection "attachment⇒user" stays, but the user only has a single meta entry

Yes.

[franz-josef-kaiser]

Done with 30378c7 and c044b60