feat(udp-core, udp-server, configuration): add trait abstractions for REST API decoupling (SI-30)

[josecelano]

Summary

Spec review for EPIC #1669 subissues SI-30 and SI-33:

SI-30 (#1924) — narrowed scope

• Now focuses on UDP-side trait extraction only (BanningStats, UdpCoreStatsRepository, UdpServerStatsRepository)
• REST-side wiring deferred to SI-33 (contract-first architecture)
• Added deep coupling analysis documenting exactly what the REST layer uses from each UDP type
• Added corrected architectural understanding (REST API is orchestrating service, not layer inversion)
• MAX_CONNECTION_ID_ERRORS_PER_IP → config option

SI-33 (#1930) — new open issue

• Promoted from draft docs/issues/drafts/1669-define-rest-api-contract-first-package-architecture.md
• Open issue created at docs/issues/open/1930-1669-si-33-rest-api-contract-first-architecture.md
• GitHub issue created: SI-33: Define REST API contract-first package architecture for EPIC #1669 #1930
• Draft file removed (preserved in git history)

EPIC.md

• Updated subissue table to reflect new SI-30 scope and added SI-33 entry
• Corrected description of rest-api-core → udp-server dependency from "layer violation" to "cross-service orchestration dep"

Pre-merge checks

• cargo machete — pass
• linter all — pass
• cargo test --doc --workspace — pass
• cargo +nightly fmt --check — pass
• cargo +nightly check --all-targets --all-features — pass
• cargo +stable test --all-targets --all-features — pass

[Copilot]

Pull request overview

This PR advances EPIC #1669 (SI-30) by extracting UDP-side trait abstractions and moving the connection-id error ban threshold from a hardcoded constant into configuration, laying groundwork for later REST decoupling (SI-33).

Changes:

• Introduces trait abstractions for UDP core/server stats repositories and banning stats.
• Replaces MAX_CONNECTION_ID_ERRORS_PER_IP with UdpTracker.max_connection_id_errors_per_ip (defaulted via serde).
• Wires the new config field through containers/examples/tests and adds async-trait where needed.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/container.rs	Plumbs max_connection_id_errors_per_ip into UDP core services init.
packages/udp-server/src/statistics/repository.rs	Adds UdpServerStatsRepository trait and implements it for the concrete repository.
packages/udp-server/examples/udp_only_public_tracker.rs	Adds the new UDP tracker config field in the example.
packages/udp-server/Cargo.toml	Adds async-trait dependency for the new trait object pattern.
packages/udp-core/src/statistics/repository.rs	Adds UdpCoreStatsRepository trait and implements it for the concrete repository.
packages/udp-core/src/services/banning.rs	Adds BanningStats trait implemented by BanService.
packages/udp-core/src/lib.rs	Removes the hardcoded MAX_CONNECTION_ID_ERRORS_PER_IP constant.
packages/udp-core/src/container.rs	Threads the configured threshold into BanService initialization.
packages/udp-core/Cargo.toml	Adds async-trait dependency for the new trait object pattern.
packages/test-helpers/src/configuration.rs	Updates ephemeral config builder with the new UDP config field.
packages/rest-api-core/src/statistics/services.rs	Removes dependency on the deleted constant in tests.
packages/configuration/src/v2_0_0/udp_tracker.rs	Adds max_connection_id_errors_per_ip config field with serde default.
Cargo.lock	Locks async-trait into the workspace dependency graph.

Comments suppressed due to low confidence (1)

packages/udp-server/examples/udp_only_public_tracker.rs:68

• This example now sets additional UdpTracker fields, but the runtime output still claims UdpTracker is only “bind address, cookie lifetime”. Updating the printed description avoids confusing users running the example.

        max_connection_id_errors_per_ip: 10,
    };

    println!("Types from torrust-tracker-configuration used by this binary:");
    println!("  Core       — tracker domain settings");

---

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[codecov]

Codecov Report

❌ Patch coverage is 56.00000% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.51%. Comparing base (94427f3) to head (637c17b).

Files with missing lines	Patch %	Lines
src/container.rs	0.00%	4 Missing ⚠️
packages/udp-core/src/services/banning.rs	0.00%	3 Missing ⚠️
packages/udp-core/src/statistics/repository.rs	0.00%	2 Missing ⚠️
packages/udp-server/src/statistics/repository.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1933      +/-   ##
===========================================
+ Coverage    79.46%   79.51%   +0.05%     
===========================================
  Files          324      324              
  Lines        23116    23137      +21     
  Branches     23116    23137      +21     
===========================================
+ Hits         18369    18398      +29     
+ Misses        4476     4468       -8     
  Partials       271      271              

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[josecelano]

ACK 637c17b