feat(telegram): support forum topic via native message_thread_id

[appleboy]

Summary

Adds Telegram forum topic support (message_thread_id) using the Bot API's native parameter instead of the HTTP-transport query-injection workaround proposed in #141.

The old go-telegram-bot-api v4.6.4+incompatible (2018, upstream archived) has no message_thread_id support, which is why #141 had to patch it in at the http.RoundTripper level. This PR migrates to the community-maintained OvyFlash/telegram-bot-api fork (the one recommended by the archived upstream), where every chat config embeds BaseChat.MessageThreadID — the parameter is only sent when non-zero, and only on actual send requests.

Changes:

• Dependency: go-telegram-bot-api/telegram-bot-api v4.6.4+incompatible → OvyFlash/telegram-bot-api (tracks current Bot API).
• New setting: message_thread_id (PLUGIN_MESSAGE_THREAD_ID / TELEGRAM_MESSAGE_THREAD_ID / INPUT_MESSAGE_THREAD_ID), applied to all message types: text, photo, document, sticker, audio, voice, video, location, venue.
• API migration (mechanical): New*Upload(user, path) → New*(user, tgbotapi.FilePath(path)), DisableWebPagePreview → LinkPreviewOptions.IsDisabled, NewBotAPIWithClient → NewBotAPIWithOptions(token, WithHTTPClient(...)) (non-deprecated form; SOCKS5 proxy path preserved).
• Docs: DOCS.md gains a forum-topic example and a message_thread_id parameter reference entry.

Related issues

• GitHub: Related to [feat] Added group threat ID support #141 (supersedes the transport-wrapper approach)

Architecture / flow

flowchart LR
    subgraph main.go
        F["--message.thread.id flag<br/>PLUGIN_MESSAGE_THREAD_ID"]
    end
    subgraph plugin.go
        C["Config.MessageThreadID"]
        E["Exec: per-recipient send loops<br/>(text/photo/document/sticker/<br/>audio/voice/video/location/venue)"]
    end
    subgraph "OvyFlash/telegram-bot-api"
        B["BaseChat.MessageThreadID<br/>AddNonZero(message_thread_id)"]
    end
    T["Telegram Bot API"]
    F --> C --> E --> B --> T
    style F fill:#d4edda,stroke:#28a745
    style C fill:#d4edda,stroke:#28a745
    style E fill:#fff3cd,stroke:#ffc107
    style B fill:#d4edda,stroke:#28a745

Loading

Green = new, yellow = modified (library migration).

AI authorship

• No AI was used
• AI was used
  • Tool / model: Claude Code (claude-fable-5)
  • AI-authored files: plugin.go, main.go, DOCS.md, go.mod, go.sum
  • Human line-by-line reviewed: None — not yet reviewed by a human.

Change classification

• Leaf change
• Core change — the library swap touches every message-send path of the plugin.

Plan reference

Replace the http.RoundTripper query-injection approach of #141 with the library's native MessageThreadID field, taking the opportunity to move off the archived v4 dependency.

Verification

• Automated: go build ./... ✅, go vet ./... ✅, go test ./... (13 tests) ✅, golangci-lint run ./... ✅ (all local)
• Manual: none
• Not run: live send to a forum supergroup topic (requires a real bot token + forum group; existing integration tests that need TELEGRAM_TOKEN run in CI)

Security check

• No secrets in the diff
• External inputs are validated (thread id parsed as int by urfave/cli; zero value omits the parameter)
• Errors do not leak internals (existing token-redaction in Send unchanged)
• N/A — no auth/permission interface changed

Risk and rollback

• Risk: the dependency migration changes the request-encoding layer for all sends (multipart upload handling, param serialization). A behavioral regression would affect every notification type, not just forum topics. Note: when message_thread_id is set and to includes non-forum chats, Telegram rejects those sends with "message thread not found" — inherent to a global thread id setting.
• Rollback: revert the single commit; no schema, config, or wire-format migration involved.

Reviewer guide

• Read carefully: plugin.go — bot construction (SOCKS5 path) and the nine send loops; confirm each sets MessageThreadID and the constructor migration is faithful.
• Spot-check: main.go flag wiring, DOCS.md wording, go.mod/go.sum (dependency swap drops technoweenie/multipartstreamer).

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds Telegram forum-topic support by introducing a message_thread_id setting and migrating the plugin from the archived go-telegram-bot-api dependency to the maintained OvyFlash/telegram-bot-api fork so the native message_thread_id parameter can be sent without HTTP transport hacks.

Changes:

• Swaps Telegram Bot API Go dependency to github.com/OvyFlash/telegram-bot-api and updates message-send call sites accordingly.
• Adds a new message_thread_id configuration/flag/env var and applies it across all outbound message types.
• Updates documentation to include the new setting and an example for forum topics.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
plugin.go	Migrates Bot API usage, wires MessageThreadID and link preview options into all send paths.
main.go	Adds CLI flag/env var wiring for message.thread.id → Config.MessageThreadID.
go.mod	Replaces archived Telegram Bot API library with OvyFlash/telegram-bot-api.
go.sum	Updates dependency checksums for the new Telegram library and removed transitive deps.
DOCS.md	Documents message_thread_id and adds a forum-topic example.

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