Tags can only be alphanumeric

[nus-se-script]

When adding a new friend, the tag given can only be alpha-numeric. This was not stated in the User Guide, and only pops up as an error message in the application.

Steps to reproduce: add n/Ivan t/friend e/betsycrowe@example.com a/Newgate Prison p/1234567 t/school-mate

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_{[original: nus-cs2103-AY2324S2/pe-interim#4093] [original labels: severity.Low type.DocumentationBug]}

[chewbum]

Team's Response

It is stated in our UG that tags should only contain alphanumeric characters.

Duplicate status (if any):

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