juju register fails with usernames that contain uppercase letters

[Felipe Reyes]

When user creates a user that contains uppercases (e.g. juju add-user JohnDoe), then the "juju register" step fails. It's not clear if juju shouldn't be accepting that kind of usernames in the first place or if it's juju register the one at fault here.

Steps to reproduce:

juju add-user TEST
juju register <HASH_GIVEN_BY_add-user>

Expected result:

the new user is able to login to the controller

Actual result:

juju register MF4TBFRFU1QwIRMOMTAuNS4wLjU6MTcwNzATDzI1Mi4wLjUuMToxNzA3MAQg9KyO-NGJ-
Enter a new password:
Confirm password:
Enter a name for this controller [stsstack-stsstack]:
ERROR Provided registration token may have been expired.
A controller administrator must reset your user to issue a new token.
See "juju help change-user-password" for more information.

This is how the user looks like the database:

{
        "_id" : "test",
        "name" : "TEST",
        "displayname" : "",
        "secretkey" : BinData(0,"9KyO+NGJ+EwqG7j7DClc9ysnODXWbzoRTp089iYw9tE="),
        "passwordhash" : "",
        "passwordsalt" : "",
        "createdby" : "admin",
        "datecreated" : ISODate("2019-06-19T16:58:06Z"),
        "txn-revno" : NumberLong(2),
        "txn-queue" : [
                "5d0a699e8c77460db2841f90_341d2785"
        ]
}

So I believe that this could be due to the mismatch between "name" and "_id". Here it is the transaction that jujud attempted to commit:

2019-06-19 17:06:51 TRACE juju.state.txn database.go:359 ran transaction in 0.028s (retries: 0) []txn.Op{
    {
        C: "users",
        Id: "TEST",
        Assert: "d+",
        Insert: nil,
        Update: bson.D{
            {
                Name: "$set",
                Value: bson.D{
                    {
                        Name: "passwordhash",
                        Value: "jCDPZS6gXBJe8p97rwfRv7X/",
                    },
                    {
                        Name: "passwordsalt",
                        Value: "+2kUw+9Q/Xudsdeg",
                    },
                },
            },
            {
                Name: "$unset",
                Value: bson.D{
                    {
                        Name: "secretkey",
                        Value: "",
                    },
                },
            },
        },
        Remove: false,
    },
}
err: transaction aborted

[Harry Pidcock (hpidcock)]

https://github.com/juju/juju/pull/10369