User is informed immediately if a duplicate email address or user name is provided

[Steffengreiner]

What was changed 1.) Complete UI Overhaul into distinct components. 2.) Remove of outdated Handler interface and implementation 3.) Replace manual validation checks with vaadin binder allowing to show an invalid input immediatly to the user. 4.) Field specific Error notifications are replaced with the error message in their corresponding fields.

Missing Invalid and valid feedback icon next to each field is not provided as of yet. To keep this PR manageable, the outdated domain logic was not touched.

[sonarcloud[bot]]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[Steffengreiner]

This is included in the SSO orcid PR #651