Mail Regex Pattern might be relaxed

[thomaschiozzi-tndigit]

The system uses an internal regex to validate email
https://github.com/scc-digitalhub/AAC/blob/5582a0f1d978b9b98cbf5acac0589910cff50c89/src/main/java/it/smartcommunitylab/aac/SystemKeys.java#L122\

The current regex is more restrictive that what suggerested by the reference RFC: https://www.rfc-editor.org/rfc/rfc5322#section-3.2.3. Even though the complete email characters space is probably not admitted in the current state (as the email is used for multiple purposes), the current regex might be relaxed to allow more special characters.