REST API username format guidelines

Currently COmanage Registry applies no rules to the CO or Platform admin that creates a REST API username. Perhaps, it would be advisable to provide guidelines to the users on what is permitted and what is not. This way we can prevent situation like:

• username ioigoume being different from Ioigoume
• username having a form like hi.....@@@@

Some indicative rules could be the following:

• Usernames can contain letters (a-z), numbers (0-9), dashes , underscores (_), apostrophes ('), and periods (.).
• Usernames can't contain an ampersand (&), equal sign (=), brackets (<,>), plus sign , comma (,), or more than one period (.) in a row.
• Usernames can begin or end with non-alphanumeric characters except periods (.), with a maximum of 64 characters.