Huge commitfest app update upcoming: Tags, Draft CF, Help page, and automated commitfest creat/open/close

The new PG19 development cycle is starting soon. So that seemed like a
good excuse to make some big improvements to the commitfest app. My
plan is to deploy these changes on the 30th of June. So that we can
start the new cycle fresh with these changes. As always feedback on
these changes is very welcome. The below will contain some links to
the staging environment both username and password for the http auth
are "pgtest".

# Introducing tags

This has been requested by many people. New tags can currently only be
created through the admin interface, but they can be assigned to a
patch by anyone. There are a bunch of tags that I added by default.
You can also easily filter patches by a specific tag by clicking on a
tag on a commitfest overview page. See the tags.png screenshot, or the
staging environment:

https://commitfest-test.postgresql.org/53/

Big thanks to Jacob for the initial work on this feature.

# Draft CF

There's now an additional Draft CF. People can move patches there as a
way of not forgetting about them. CFBot will rerun these patches less
frequently (exact behaviour TBD). Draft CFs are never "In Progress"
and are open until the final CF of the release cycle becomes "In
Progress". So PG19-Drafts will close on February 28th 2026, and at the
same moment PG20-Drafts will be opened.

Big thanks to David G Johnston for the initial work on this feature,
and early review/feedback on all my changes to it.

# Automated commitfest open/close/create

Right now people manually have to open/close/create commitfests at our
regular cadence. This now actually encodes this cadence in the app
itself. A new open commitfest is automatically created when needed. As
well as commitfests automatically getting started or closed. The only
commitfest that's not fully automated is the last one of the cycle,
since that ends when the feature freeze starts (and the feature freeze
isn't always the same date). To handle that the RMT (or anyone with
access) should change the enddate of the final commitfest in the admin
interface to the new date. That will need to happen before March 31st.

A *bikesheddable* change here is the names that the newly created
commitfests get automatically. Given we now have a Drafts commitfest,
it seemed reasonable to align the naming of the regular commitfests
with that. The draft commitfest will be called:

- PG19-Drafts

And our already well-known commitfests for PG19 will be called as follows:

- PG19-1 (previously 2025-07)
- PG19-2 (previously 2025-09)
- PG19-3 (previously 2025-11)
- PG19-4 (previously 2026-01)
- PG19-Final (previously 2026-03)

The dates will be the same, the name will simply not be of the
{year}-{month} format anymore. The actual dates will still be easily
visible though. So the intent is that no-one loses information, but
instead people will gain information because it's clear what Postgres
version a commitfest is about.

# New homepage

The homepage is revamped. It now shows only "In Progress", "Open",
"Draft" and "Previous" commitfests and it also shows names & dates for
"Next open CF" and "Final CF of the release cycle". See homepage.png
screenshot for details or go to
https://commitfest-test.postgresql.org/

The full list of commitfests is still available at:
https://commitfest-test.postgresql.org/commitfest_history/ This page
is linked to at the bottom most link on the homepage.

# Help Page

There's now a help page for new users which explains how this app is
used and what certain terminology means:
https://commitfest-test.postgresql.org/help/

# Small fixes

Flonents Tselai made wiki and git links display correctly.