Add PVC for agent

[pat-s]

To persist /etc/woodpecker/agent.conf and solve woodpecker-ci/woodpecker#3023

To clean old agents, the following commands can be executed on the database (Postgres example)

delete from agents where capacity=-1;
delete from agents where coalesce(name, '') = '';

This will clean a lot stale agents but not all.

Another way is to clean all agents for which the last contact is older than 1 day (thanks @zc-devs), one can do

delete from agents where last_contact < now() - interval '1 day';

Alternatively, one can remove all agents, then recreate the pod and the attached PV. This will reinitialize a fresh agent with a new ID.

I've tested this PR and recreated the agents (two replicas) many times. No new agents were created and /etc/woodpecker/agent.conf always showed the persistet agent ID.

[pat-s]

@zc-devs @ymettier This will fix the agent registration issue. Any comments/suggestions?

[zc-devs]

To clean old agents, the following commands can be executed on the database

Maybe it worth to mention query like

delete from agents where last_contact < now() - interval '1 day';

^ not tested.

[pat-s]

ping @anbraten

[pat-s]

@xoxys Added yamllint, prettierc, addressed all warnings and your comments.

[xoxys]

LGTM

[dunn]

is this supposed to be 1Gi?

[xoxys]

Why? The volume just holds the agent configuration (text file). 1Mi should be more than enough as default.

[dunn]

it's 1Gi in the agent subchart values (https://github.com/woodpecker-ci/helm/pull/163/files#diff-afab925868b45a9b5ea72b370133adf7a55e74652cfd7695bbeca6b7e2c30658R65) and i think 1Mi is below the minimum of some csi provisioners

[xoxys]

Ok yes, missed that. Good point in that case we should fix it.