Get code base working with Xcode 12

[timbms]

New regression checklist

• I updated the iOS openHAB app to the latest TestFlight version.
• I read the Contribution Guidelines
• I searched for existing GitHub issues

Describe the bug
Code base needs to be updated to work with Xcode 12 without warnings and errors:

• Resolve Validate project settings: update to recommended settings
• Resolve : 'SessionDelegate' has different definitions in different modules; first difference is definition in module 'Alamofire.Swift' found method

To Reproduce

• Check out current version
• Compile with Xcode 12
  Expected behavior
  No more compile errors and warnings

[weakfl]

@timbms I think I've already fixed all the warnings in develop.

The SessionDelegate problem is an Xcode bug, but can be worked around by renaming it in the KingFisher pod for now.

[timbms]

@weakfl I overlooked your commits. Thank you for them
With respect to SessionDelegate we should make the current work around transparent to everybody
Then we could close the ticket

[weakfl]

@timbms agreed. Looks like migration to Alamofire 5.2 is required though.

[timbms]

The workaround is to rename "SessionDelegate" to "KFSessionDelegate" in Kingfisher's Core/ImageDownloader.swift and Core/SessionDelegate.swift as explained in onevcat/Kingfisher#1517.

[weakfl]

@timbms I ment the workaround isn't required anymore with Alamofire 5.2 and latest Kingfisher. What's the state of the Alamofire 5 branch?

[timbms]

@weakfl I fully understood you that you would rather jump to Alamofire 5. But so far, the branch is not ready. In particular the client certificate handling is not migrated to Alamofire 5 yet.
In my understanding of Alamofire 5's handling of client certificates (see Alamofire/Alamofire#2993), it would be sufficient to change the ClientCertificateManager to load the certs into SessionConfiguration.urlCredentialStorage. Maybe you can have a look

[timbms]

onevcat/Kingfisher#1530 resolved in Kingfisher 5.15.4. Therefore we will make this update

[weakfl]

@timbms That's good news, gives us some time to update Alamofire...