Upgrades Gitea's Telegram webhook integration to support Telegram Bot
API 10.1 (June 2026 release). This enables Gitea webhooks to take
advantage of rich formatted messages (tables, nested blocks, collapsible
details, etc.) by routing them through the /sendRichMessage endpoint
with the new rich_message payload structure.
Old `/sendMessage` webhook URLs are written to `/sendRichMessage`
at runtime to prevent the need for database migrations
Fixes https://github.com/go-gitea/gitea/issues/38118
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
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