V1 support branch

[muhlemmer]

We have recently release V2 on main, which brings many breaking changes. There are requests to maintain a V1 branch for the time being. At Zitadel we have nothing against it, however there is a "policy" we would like to share:

• V1 will be branched from the latest tag.
• It will receive security and (simple) bug fixes.
• Community should lead contributions to the V1 branch. Zitadel members will do the reviews as usual.
• There is no specific timeline (yet) but as long as people will send fixes, we don't mind merging them.
• No new features, those should target main.
• Breaking changes should target next.

The above should off course be integrated in the contribution guidelines, which we will do in due time.

I will create the fork today and will take care of some first (urgent) chores:

• drop Go support <1.18 : x/text updates don't build against older releases.
• update all modules. Due to the above, some dependabot PRs couldn't be merged into V1 / old main.
• auto releases
• branch protection

From there on, it should become a community effort.