plugins/sql: allow datetime functions

[JosephGoulden]

Hi. I'm using the SQL plugin to perform analytics on my node. It would be very useful to be able to use the date/time functions so that only the required data is returned.

I've written some queries to test this change and it works as expected.

[niftynei]

Please remove keyword args from the functions list.

Also remove the unnecessary Merge commit 797cdc8.

[rustyrussell]

These look safe, thanks!

Two changes, if you could:

1. Can you add a line to the commit message so this gets mentioned in the CHANGELOG for the release? Like so:

Changelog-Changed: Plugins: `sql` now allows date and time sqlite functions.

2. Can you edit doc/schemas/lightning-sql-template.json to include these in the list of allowed functions? That's the basis for our documentation generation.

Thanks!

[JosephGoulden]

CI failed so I generated contrib/msggen/msggen/schema.json and checked that in as well.

[rustyrussell]

CI failed so I generated contrib/msggen/msggen/schema.json and checked that in as well.

That's what CI is for :) Good catch. Changelog is a bit weird, but Release Captain will fix it up when compiling CHANGELOG.md.

Ack dc0ae31