feat: support defining MySQLi flags

[wilr]

Description

Adds the ability to define mysqli flags (and socket) see #9394

Manual testing steps

To test this locally, you can set this via config.yml and verify in the MySQL connector that the flag is present

SilverStripe\ORM\Connect\MySQLiConnector:
  flags:
    - MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT

Issues

• Pass additional flags into MySQLi::real_connect #9394 Pass additional flags into MySQLi::real_connect #9394

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[GuySartorelli]

It seems weird to use config for this when everything else about a database connection is declared using env vars. Can you please explain your thinking here?

[wilr]

All the other db specific values ssl_cipher_default, connection_charset are config values so lets keep consistent

[GuySartorelli]

I feel like the socket you're using to connect has more to do with the environment-specific infrastructure, while the charset your connection uses is more to do with how the data is stored.

i.e. you want the data to be consistent regardless of what you're connecting to - but each environment may want to connect to a database on a different port.

[wilr]

Yeah either or. Though you can always set config based on env vars so config gives a bit more flex.

[GuySartorelli]

I would prefer for everything to do with what database you're connecting to to be consistent. For CMS 5 that means explicitly using ENV vars.

We can change it in CMS 6 to use config which defaults to those env vars, if you want config.

[wilr]

Sure so SS_DATABASE_SOCKET How do you imagine the SS_DATABASE_FLAGS to work? I don't think it would function as a string.

[GuySartorelli]

We could either introduce some functionality to allow array values from env vars, or more simply, just use a comma (or other character) delimited string. Split by the delimiter, use constant() like you're doing below to get the specific flags based on the names.

[wilr]

Updated to env vars

[GuySartorelli]

LGTM and works as expected. Thanks!

Could you please also open a PR to update the changelog and add the new env vars to the env vars list?

[GuySartorelli]

This isn't super easy to read but I won't ask for you to change it now. Just something to think about for next time.