Add chat_id_file configuration parameter for Telegram

[tennisleng]

This PR adds support for reading chat_id from a file, similar to bot_token_file. This allows users to securely pass chat_id using secrets or volumes in docker-compose without exposing it in cleartext in the config file.

Changes

• Added ChatIDFile field to TelegramConfig struct
• Updated validation to require either chat_id or chat_id_file (but not both)
• Added getChatID() method to read chat_id from file
• Updated Notify() method to use the new getChatID() method

Testing

• Follows the same pattern as bot_token_file
• Validates that either chat_id or chat_id_file is provided
• Validates that both are not provided simultaneously
• Reads and parses chat_id from file as int64

Fixes #4672

[ultrotter]

Do we expect the contents to change as we go? Would we consider saving the chatID to n.conf.ChatID after we read it, and then in this function return that one first, and only read the file if ChatID is still 0?

[tennisleng]

I've added the caching you suggested - getChatID() now returns the cached value first and only reads from file if ChatID is still 0, then caches it for future calls. This avoids the file I/O on every notification

[ultrotter]

I think you removed this improvement when you removed the unrelated changes from the branch... You could cherry-pick just this one patch on top, or push to a version that has just those.

[ultrotter]

Please can you remove the unrelated changes from this branch? Otherwise I don't think it can be merged, as is...

Thanks!

G

[TheMeier]

If chat_id is considered a secret it also get mapped to a secret type. Right now it is mapeed to int and is visible unmasked in /#/status

[TheMeier]

related #2498