chatmail-metadata warns about unknown requests

[link2xt]

There are many warnings that look like this:

Sep 03 02:20:20 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U1\tpriv/909972312f56d666527204003dd4fc98/comment'
Sep 03 02:20:20 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U2\tshared/909972312f56d666527204003dd4fc98/comment'
Sep 03 02:20:21 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U3\tpriv/28b3ff10bd55d6663c5604003dd4fc98/comment'
Sep 03 02:20:21 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U4\tshared/28b3ff10bd55d6663c5604003dd4fc98/comment'
Sep 03 02:20:34 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U1\tpriv/e8989a394356d666c47504003dd4fc98/comment'
Sep 03 02:20:34 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U2\tshared/e8989a394356d666c47504003dd4fc98/comment'
Sep 03 02:20:47 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U1\tpriv/707f35175356d666d77704003dd4fc98/comment'
Sep 03 02:20:47 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U2\tshared/707f35175356d666d77704003dd4fc98/comment'
Sep 03 02:20:48 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U3\tpriv/2808e30f0756d666016a04003dd4fc98/comment'
Sep 03 02:20:48 chatmail-metadata[2795551]: WARNING:root:unknown dictproxy request: 'U4\tshared/2808e30f0756d666016a04003dd4fc98/comment'

U means "unset" according to https://doc.dovecot.org/2.3/developer_manual/design/dict_protocol/#dovecot-dict-protocol
As far as I see we don't handle "unset" at all.

Not sure what causes these unset commands. Maybe this happens when user or folder is created. I think we should handle "unset" for all keys by doing nothing and reporting "O" (ok) status or "F" if it is some key that we want to return and make it impossible to unset.

[missytake]

It doesn't seem to happen on nine anymore, the last log messages about it are from May 19 (though newer ones might have been lost to log rotation?). Do you remember on which server this happened?

Otherwise I suggest to close this issue. It doesn't seem to cause problems anyway other than log messages, so the "bug" label might not apply.

[link2xt]

I think it was actually fixed at some point, maybe during dictproxy refactoring.
And Dovecot 2.4.0 removed dictproxy anyway: #476