Support syncing rego rules from Git

For some users it might be more convenient to have their rego rules in a Git repo instead of having to put them in ConfigMaps.
For this we could copy the git-sync mechanism in Airflow to OPA servers.

Tasklist

• The first task is to make a decision (ideally as an ADR) if we want to have this functionality at all (e.g. check security aspects or our abstraction layer that we will create)
• Check if OPAL helps up

从提议的 ADR 开始：评估是否应支持从 Git 同步 Rego 规则，包括其安全影响以及所需的抽象层。比较 Airflow 的 git-sync 机制，并调查 OPAL 是否有帮助。记录清晰的决策及其依据后，即视为完成。