implement GPG directly in k9

[webratte]

Checklist

• [X] I have used the search function to see if someone else has already submitted the same feature request.
• [X] I will describe the problem with as much detail as possible.
• [X] This issue only contains a request for one single feature, not multiple (related) features.

App version

all versions

Problem you are trying to solve

It wuold be great to implement GPG directly into k9 without the need to use openkeychain. Because it's not developed anymore.

Suggested solution

Maybe a similar solution as Delta Chat used: https://github.com/deltachat/ https://github.com/deltachat/deltachat-android

Screenshots / Drawings / Technical details

No response

[vanitasvitae]

If you need an OpenPGP library, I happen to be the author of PGPainless and I'd love to assist you :)