Language Per Discord Webhook

[aussig]

In the current implementation, the Discord language applies to all webhooks. It would be more useful to be able to set a language per webhook.

Leave the current overarching language selector in place:

• Add an override checkbox to apply to all webhooks.
• When adding a new webhook, use the language chosen in the main selector.

[aussig]

The text is currently created once first, and then passed into the Discord class for posting. Instead, we'll need to re-work the way the text is generated so that it is done each time per webhook.

One way would be to pass in a dict containing text in all languages, but that is overkill as only one or two languages are likely to be used.

Better approach is to pass in a callable to the discord posting functions, which is called to fetch the text in the appropriate language as the posting function iterates through each webhook.