Adjust application data endpoint for verein360

[f1sh1918]

Is your feature request related to a problem? Please describe.
Add a field "isAlreadyVerified" to the application endpoint and make sure this endpoint is used correctly.

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 isAlreadyVerified field is set to true, the api token must be set in auth header: Will be done in: Verein360 application data endpoint protection #1790

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

check the documentation of the endpoint: https://github.com/digitalfabrik/entitlementcard/tree/main/docs/verein360-enpoint.md