fix ulid regex

[r0ots]

Ulid regex is not restrictive enough and can capture longer strings than expected.

[0-9A-HJKMNP-TV-Z]{26}

With this regex, an ulid like01ARZ3NDEKTSV4RRFFQ69G5FAVA is considered valid.
This contains 27 chars, but at least 26 are validating the regex, so this returns true.

Adding ^ at the start and $ at the end ensures that the regex only validates exact matching strings.

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[nathanchapman]

@colinhacks able to merge this soon?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[nathanchapman]

#2820 no joke 🥴