API first approach

[jensg-st]

At the moment the API has swagger configurations but it is an implementation-first approach. This can lead to discrepancies between implementation and swagger documentation.

The API should be build on swagger first and the implementation needs to follow. That guarantees a consistent documentation and implementation.

[jensg-st]

• Secrets search query is not correct, the query is in the URL in stead of a query param
  /namespaces/{ns}/search/secrets/{name:.*}

• Overwrite secrets wrong description
  "namespace has been successfully overwritten" instead of "secret has been successfully overwritten"