Information about fields requirements

[eMKejTestingWarriors]

💡 Describe your idea

It is fine, if user know earlier how long should be a value in a field or which characters he can use in the field.

🔬 Motivation

For example, a user in a java client should have information, that username should have max 20 characters. Also an information that a user cannot use in that field digits, capitals or special characters would be useful.

[AntumDeluge]

Java client is being outmoded & this may not qualify as being necessary to fix.