Multiple POST calls should only create 1 entry for applications

[Ultimatum22]

Is your feature request related to a problem? Please describe.
When using the API it is possible to add duplicate entries. For example, I use this to populate the server with default applications when installing with Ansible.

Describe the solution you'd like
If you use the API to create an application and the name already exists it should throw a 400 bad request.

Describe alternatives you've considered
Another option is to read the GET application and then check if the application is already present but that is too much of a hassle.

Additional context
This issue could be for more API calls, I haven't checked it because I am only using the application endpoint.

Are you open for a PR if this is a good feature, it's not that difficult to implement.

[jmattheis]

Hmm, I'm not sure. There can be valid use-cases for applications with the same name.

The client api functions similar, but it's required to work that way, because for most clients a more or less static client identifier (user-agent or device manufacturer) is used.