I am writing an iOS app that will use data from Skype for Business, and am following the guide from Microsoft called Create an application, which must be done before being able to use the API's.
What is unclear to me is when exactly to create an application? Is it:
The application here is more a kind of "virtual object (the application)" which needs to be created here, until you can start using Skype for Business (SfB) features.
So your question isn´t that easy to answer as its not clear what you wish to perform (e.g. did you wish to login, perform some task and then logoff again?). So it depends a little bit on your application and which features you are using. Therefore its no "only once ever" as the "virtual object (the application)" is destroyed at some time (e.g. your application crash and the SfB server no longer got a "yes we are still here and are listening" requests). This is controlled by the lifetime of a token which is eight (8) hours for authenticated users so you need to renew that or your application will stop working. So its more a "per taskuser & login & time" approach...
Microsoft explained the above as well in the following statement: "This is how you register your application with UCWA 2.0 as an agent of the user whose credentials you obtained in a previous step."