Target SDK level 29

[daniele-athome]

As of Google Play policy: https://support.google.com/googleplay/android-developer/answer/113469#targetsdk

Behavior changes for API 28: https://developer.android.com/about/versions/pie/android-9.0-changes-28
Behavior changes for API 29: https://developer.android.com/about/versions/10/behavior-changes-10

• FOREGROUND_SERVICE permission
• Starting in Android 9, Crypto JCA provider has been removed. Calls to SecureRandom.getInstance("SHA1PRNG", "Crypto") will throw NoSuchProviderException.
• access to DNS server properties (for Smack)
  forum thread
  possible fix: use this class for API level 21+
• privacy changes related to external file storage (should be ok, but needs testing)
• android.preference is deprecated
• verify that ANDROID_ID setting (for use as the JID resource part) is still working
• MaterialDialogs accesses some internals which might be forbidden/non-existant

Not related to targeting, but affects the app anyway:

• https://android-developers.googleblog.com/2018/03/cryptography-changes-in-android-p.html (using Bouncy Castle)

E/System: ******** DEPRECATED FUNCTIONALITY ********
E/System: * The implementation of the Signature.SHA256WITHRSA algorithm from
* the BC provider is deprecated in this version of Android.

[daniele-athome]

Finally closed in 40096a6.