* Reject emails within angle brackets
mail.ParseAddress is RFC-compliant, which means that it accepts emails
with names, as in "Billy Bob <billy@example.com>". It even accepts this
form *without* a name; e.g. "<billy@example.com>". We want to store the
plain address, so we compare the user input with the Address field of
the result from mail.ParseAddress, which should contain only
"billy@example.com", thus only accepting emails that do not contain
names nor angle brackets.
* Log a warning for admins with clear next steps
* Fix wording of comment
* And a typo
* Add specific command example to log message
* Add input email to log message
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Co-authored-by: Mattermost Build <build@mattermost.com>
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