Include screenshot URL to Telegram message

[yuri-tceretian]

Currently, Telegram integration sends two messages when an alert has a screenshot attached to it.
However, Grafana screenshot service can upload screenshots to a remote host and provides URL to the image in the alert.

When Grafana is configured this way, we probably can let users control how screenshots are sent by Telegram integration: add URL to the first message or send it as the second message.

[iBug]

If the original reasoning was

(sendPhoto API) does not present long messages well.

Then is it an option to combine image and text into one message when the text is short, and only send them in separate messages when the text is long?

[Kot-o-pes]

+1, if it worked in 8.5 grafana why it regressed in 10?

[yuri-tceretian]

I think this would be a good first issue. If someone is willing to take it, I promise to give prompt reviews.

[nutmos]

I opened a new PR #240 for this issue.