This change solves the User's API problem when you want to create an user that its email hasn't been verified yet but it exist.
At now, you can resend invitation email using endpoint /users/{id}/resend-invitation
Fixes#184
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)
Admin API now requires a 128 byte base64 encoded secret to be passed in
Authorization header, closing up a potential security hole for those
who expose this service.
