Documentation about API v2 (#1210)

* Mention API v2
Mention v2 API in docs

* Import ADR for git reader

* Update docs/adr/adr_008_git-readers.md

Co-authored-by: Alex Cottner <148472676+alexcottner@users.noreply.github.com>

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Co-authored-by: Alex Cottner <148472676+alexcottner@users.noreply.github.com>

Author: leplatrem