Migrate delegate callbacks to an observer pattern

[fethica]

Highlights

• API: Switched from delegate callbacks to an observer pattern (one-to-many). Implement FRadioPlayerObserver and call addObserver/removeObserver.
• Streams: Added support for non-live (file) streams with duration/currentTime updates, seeking, and more robust state handling.
• Packaging: SPM-only. Removed CocoaPods/Carthage files and Travis CI.
• Swift version: Bumped to Swift tools 5.5 (Xcode 13+).
• Demo app: Revamped SwiftUI-only demo (iOS 15+):
  • Reorganized into Views/Models/Resources; cleaner UI; uses AsyncImage for artwork.
  • Generated with XcodeGen (no .xcodeproj in repo).
• CI: Added GitHub Actions
  • spm.yml builds and tests the library.
  • demo.yml generates (XcodeGen) and builds the demo.

Migration notes (delegate → observers)

• Before (delegate, one-to-one):
  player.delegate = self
• Now (observers, one-to-many):
  player.addObserver(self) // conform to FRadioPlayerObserver
  // optionally: player.removeObserver(self)

Observer callbacks to implement

• radioPlayer(_:playerStateDidChange:)
• radioPlayer(_:playbackStateDidChange:)
• radioPlayer(_:itemDidChange:)
• radioPlayer(_:metadataDidChange:)
• radioPlayer(_:artworkDidChange:)
• radioPlayer(_:durationDidChange:)
• radioPlayer(_:playTimeDidChange:duration:)

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This discussion was created from the release Migrate delegate callbacks to an observer pattern.

[urayoanm]

Nice job @fethica

I think we need update Swift Radio Pro as well. Let me know if I can help

[fethica]

Hey @urayoanm, thanks! Yes, I have some local changes on the dev branch. I'll try to push them soon. I plan to remove all storyboards and start migrating the app to SwiftUI after that. I'll ping you when it's ready 😄