AES GCM SIV is not working properly on android API version 29 and older.

[juergw]

When using AES GCM SIV keys under android using the API version 29 or older, then primitive returned by Tink doesn't use AES GCM SIV, but uses AES GCM.

This is due to a bug in Android that was fixed here:
https://android.googlesource.com/platform/external/bouncycastle/+/14ceec126e49f2f4748f0d540be820515cc725a6.

We will fix this by adding a check and returning an error if AES GCM SIV is used on android 29 or older.

If this causes an issue for you, let us know.