The DB implementation expects secrets to be base64 encoded blobs.
Because of this a bunch of tests broke moving to sqlite.
A lot of this commit is fixing those tests.
This commit moves the user.Manage to its own package (user/manager)
so it can import the connector package in a later commit.
For clarity, it renames "Manager" to "UserManager" using gorname.
This commit has no functional changes.
Invite emails are essentially just reset password emails with a
different template (though this can and probably will change (slightly)
in the near future)
