rss: Replace crashy double-formatting with standard format_token_replace

[progval]

No description provided.

[examknow]

Suggested change

	template = channel.get_setting("rss-format", "$longtitle: $title by $author - $link")
	template = channel.get_setting("rss-format", "${longtitle}: ${title} by ${author} - ${link}")

[progval]

that's also a breakage for existing configs, isn't it?

[examknow]

I don't think custom formatting really gets used tbh, but some way to detect/migrate it would be good

[examknow]

Perhaps we could perform a sweep of the rss-format configs at module load time and convert $variable and {variable} to ${variable} and then set a bot config value to note that the migration has happened. I can't think of a nicer way to do this without majorly overcomplicating things.

[examknow]

The following should be sufficient for migration of old configs. Just place it inside the BaseModule subclass.

import re

def _migrate_formats(self):
    count = 0
    migration_sub = re.compile(r"(?:\$|{)+(?P<variable>[^}\s]+)(?:})?")
    old_formats = self.bot.database.execute_fetchall("""
        SELECT channel_id, value FROM channel_settings
        WHERE setting = 'rss-format'
    """)

    for channel_id, format in old_formats:
        new_format = migration_re.sub(r"${\1}", format)
        self.bot.database.execute("""
            UPDATE channel_settings SET value = ?
            WHERE setting = 'rss-format'
            AND channel_id = ?
        """, [new_format, channel_id])
        count += 1

    self.log.info("Successfully migrated %d rss-format settings" % count)

def on_load(self):
    if self.bot.get_setting("rss-fmt-migration", False):
        self.log.info("Attempting to migrate old rss-format settings")
        self._migrate_formats()
        self.bot.set_setting("rss-fmt-migration", True)

[examknow]

Tested and working