Ability to add apps for users on their behalf

**Is your feature request related to a problem? Please describe.**

I have users of gotify who are purely on the "receiving side", in the sense that they receive notification and act upon them, but are not technically apt to create their own applications.

On the other hand (and thankfully), whatever application is added to their account (see below) immediately appears on their phone. This is great.

This means that I have to keep the passwords for their users handy, then impersonate them to create an app (and copy the API key)

**Describe the solution you'd like**

An "users admin dashboard" where I could, from my admin account, create the applications for them (and have access to the API keys which then are used in my applications)

**Describe alternatives you've considered**

Keeping their passwords handy and using incognito mode to connect on their behalf.