I need to check that a proper username is entered in the custom signin form on my web site to pass it to Auth.signUp method of aws-amplify.
Things like minimum/maximum number of characters and allowed characters.
Documentation at this link does not help, please point me to a correct page, thank you!
See AWS SDK for validation rules.
The username for the user. Must be unique within the user pool. Must be a UTF-8 string between 1 and 128 characters. After the user is created, the username can't be changed.
Not perhaps a perfect description but has at least the minimum and maximum character count.
Edit: Cognito API reference reveals that regex pattern for username validation is: [\p{L}\p{M}\p{S}\p{N}\p{P}]+
https://docs.aws.amazon.com/cognito-user-identity-pools/latest/APIReference/API_AdminCreateUser.html
BTW, username cannot be changed after creation so perhaps you want to use preferred_username attribute to store the username which a user submits in sign in form (and make back-end to generate a value for username automatically (uuid for example)).
The document behind the link states:
Activate the preferred_username attribute so that your user can change the user name that they use to sign in while their username attribute value doesn't change.