feat(mtproto): add MTPROTO backend type and Mtproto proxy

[T3ST3ST3R0N]

Syncs the bridge with the new MTProto backend in PasarGuard/node (PR #61).

Changes

• proto: BackendType.MTPROTO, a Mtproto proxy message (secret, user_ad_tag, max_tcp_conns, max_unique_ips), and Proxy.mtproto
• regenerated common/service.pb.go and common/service_grpc.pb.go
• common/funcs.go: added CreateMtproto(secret, userAdTag, maxTcpConns, maxUniqueIps) and extended CreateProxies with the mtproto argument

Notes

Data quota and expiry are intentionally not part of the message. The panel owns quota and expiry enforcement (usage reporting plus user sync), the same as for the xray and wireguard backends, so the node never hands them to telemt.

CreateProxies gains a trailing mtproto *Mtproto argument, so callers must pass it (use nil when not configuring MTProto).

Summary by CodeRabbit

• New Features

  • Added support for an additional proxy/backend option, including configuration fields for MTProto.
  • Proxies can now carry MTProto settings alongside existing connection types.

• Tests

  • Updated test setup to include the new proxy configuration format.

[coderabbitai]

Walkthrough

Adds MTProto as a new backend type: MTPROTO = 2 is added to the BackendType enum, a new Mtproto message is defined in service.proto, and Proxy gains a mtproto field. CreateMtproto factory function is added and CreateProxies is extended with an mtproto *Mtproto parameter. The test fixture is updated to pass nil for the new argument.

Changes

MTProto Backend Addition

Layer / File(s)	Summary
Proto schema: Mtproto message and BackendType enum common/service.proto	Adds MTPROTO = 2 to BackendType, introduces Mtproto message with secret, user_ad_tag, max_tcp_conns, max_unique_ips fields, and adds mtproto as field 7 on Proxy.
CreateMtproto constructor and CreateProxies signature common/funcs.go	Adds CreateMtproto factory function and updates CreateProxies to accept and populate the new mtproto *Mtproto parameter on the returned Proxy.
Test fixture call site update bridge_test.go	Passes nil as the new mtproto argument in the CreateProxies call for the user fixture.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐇 A new tunnel hops into the fray,
MTProto joins Wireguard today.
A nil slips in where the message will go,
Secret fields lined up in a row.
The rabbit nods — the proxy's complete! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: adding an MTPROTO backend type and Mtproto proxy support.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[T3ST3ST3R0N]

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🧹 Nitpick comments (1)

bridge_test.go (1)

69-69: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Add one positive MTProto fixture path.

This update only preserves the pre-existing nil path, so the new CreateMtproto(...)/Proxy.Mtproto wiring still has no direct test coverage. A small test that passes a non-nil MTProto config and asserts it survives CreateProxies/CreateUser would catch future regressions cheaply.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@bridge_test.go` at line 69, Add a positive MTProto test case alongside the
existing nil path in bridge_test.go so the new CreateMtproto and Proxy.Mtproto
wiring is actually exercised. Update the relevant bridge test around
CreateProxies and CreateUser to pass a non-nil MTProto config, then assert the
resulting proxy/user state preserves that configuration instead of only covering
the nil case. Use the existing CreateMtproto, CreateProxies, and CreateUser
symbols to anchor the new coverage.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@bridge_test.go`:
- Line 69: Add a positive MTProto test case alongside the existing nil path in
bridge_test.go so the new CreateMtproto and Proxy.Mtproto wiring is actually
exercised. Update the relevant bridge test around CreateProxies and CreateUser
to pass a non-nil MTProto config, then assert the resulting proxy/user state
preserves that configuration instead of only covering the nil case. Use the
existing CreateMtproto, CreateProxies, and CreateUser symbols to anchor the new
coverage.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 77b5f85e-b105-4c0a-be20-e9dd6d7f2fef

📥 Commits

Reviewing files that changed from the base of the PR and between d70a9eb and fbe88da.

⛔ Files ignored due to path filters (2)

• common/service.pb.go is excluded by !**/*.pb.go
• common/service_grpc.pb.go is excluded by !**/*.pb.go

📒 Files selected for processing (3)

• bridge_test.go
• common/funcs.go
• common/service.proto