setup argparse & logging

Setup Tests, Coverage & CI ; update tooling.

update aiohttp use and docs

Co-authored-by: Sven Seeberg <mail@sven-seeberg.de>

Co-authored-by: Sven Seeberg <mail@sven-seeberg.de>

Simplify code

Keeps the "happy path" on the function's base indentation level.

Avoids carrying status and return value variables, pre-filled in
anticipation of an error, along.

Avoids explicit setting of JSON content type, handles serialization to
JSON.

Merges duplicated code.

https://python-markdown.github.io/extensions/extra/

To get <pre> tags on fenced code