cli, sql: allow usernames to start with digits

[georgebuckerfield]

Allows CockroachDB usernames to start with digits.

Fixes #42155.

e.g.

root@:26257/defaultdb> create user '1234';
CREATE USER 1

Time: 6.698583ms

[cockroach-teamcity]

This change is 

[knz]

@georgebuckerfield thanks for your contribution!
Note: you forgot two update two tests for the new error message.

@bdarnell @mberhault @mjibson please check whether this new username format is compatible with the various other things we care about: Kerberos auth, TLS certs, CockroachCloud auth, etc.

[georgebuckerfield]

Thanks @knz - just pushed a fix for those failing tests.

[mberhault]

That's fine for x509 certs, you can generally do UTF8 up to ridiculous lenghts. CC doesn't have any particular requirements on the SQL username.

[knz]

I'm going to cautiously green light this change, even if it happens to not be compatible with some subsystem. I'd rather document known limitations (and later fix them) than prevent integration with systems where numeric usernames are prevalent.

@georgebuckerfield thank you again for your change.

bors r+

[knz]

@georgebuckerfield just a small note: I have amended your branch to make the commit comply with our general style and requirements:

• squash commits that pertain to a single unit of change
• include a before/after explanation in the commit message
• include a release note for user-facing changes

If you intend to contribute more to CockroachDB, I recommend you to consult the git commit template produced by default upon git commit, as well as https://wiki.crdb.io/wiki/spaces/CRDB/pages/73072807/Git+Commit+Messages and https://wiki.crdb.io/wiki/spaces/CRDB/pages/186548364/Release+notes

Best regards

[georgebuckerfield]

Thanks @knz! Sorry, I was waiting to see if there were any changes needed before squashing the commits. And noted re: the commit message.

[knz]

Sorry, I was waiting to see if there were any changes needed before squashing the commits.

Don't be sorry! I understood about the same. But since I don't recall you have a permission to merge yet there was no clear synchronization point for you to do this after the review and the CI results came positive.

[craig]

Build succeeded

• GitHub CI (Cockroach)

[bdarnell]

I'm going to cautiously green light this change, even if it happens to not be compatible with some subsystem. I'd rather document known limitations (and later fix them) than prevent integration with systems where numeric usernames are prevalent.

I agree with this. If names starting with digits don't work in some integrations, we can just document that and move on. (But note that the reason this request came up was for integration with a kerberos system that already contains numeric usernames, so we know that kerberos/gssapi already supports this in general)

One thing worth testing: names starting with digits generally have to be quoted when used in SQL (for example in GRANT statements). We should make sure we have tests that numeric user names work as expected once created.