Application data verification

[f1sh1918]

Is your feature request related to a problem? Please describe.
The application data send by verein360 has to be validated before building data structure and store it in the database

Describe the solution you'd like

• check that all mandatory fields have data
• birthday >= 16 years
• email address must be valid format
• regionIdentifier must exist in the database (regions table), bring the identifier in the correct format first (leading zero and only 4 digits)
• organization contact person and applicant can't be the same
• workSince: >=2years

if the validation of a field fails, send an error response with information what is incorrect

blocked by: #1620