feat(configuration): move v3 network settings per tracker instance (#1640)

[josecelano]

Summary

Implements the v3 schema slice of issue #1640 (subissue #3 of EPIC #1978).

Each HttpTracker and UdpTracker in v3 now carries its own network: Network block containing external_ip, on_reverse_proxy, and ipv6_v6only. The shared [core.net] section is removed from v3. Schema v2 is unchanged.

Changes

• packages/configuration/src/v3_0_0/network.rs — Network struct with per-instance fields; #[serde(deny_unknown_fields)] to reject old v2 field names at deserialization
• packages/configuration/src/v3_0_0/http_tracker.rs — replaced flat ipv6_v6only: bool with network: Network
• packages/configuration/src/v3_0_0/udp_tracker.rs — same as http_tracker
• packages/configuration/src/v3_0_0/core.rs — removed net: Network field; #[serde(deny_unknown_fields)] blocks old [core.net] key
• packages/configuration/src/v3_0_0/mod.rs — updated defaults, removed get_ext_ip(), added deserialization tests including rejection of removed v2 layouts
• docs/adrs/20260721000000_make_network_configuration_per_tracker_instance.md — new ADR documenting the decision
• docs/adrs/index.md — ADR index entry
• docs/issues/open/1640-1978-per-http-tracker-on-reverse-proxy-setting.md — spec updated with schema boundary, deferred tasks, and progress log

Schema compatibility boundary

• v3 structs use #[serde(deny_unknown_fields)] — old v2 field names ([core.net], flat ipv6_v6only) are rejected at parse time
• v2 schema is untouched
• Runtime consumers (AnnounceHandler, http-core, test-helpers, app wiring) are not changed here — deferred to issue Configuration overhaul final cleanup: remove global re-exports, migrate consumers to explicit versioned imports #1980

Testing

44 unit tests pass in torrust-tracker-configuration. New tests cover:

• Deserializing [http_trackers.network] / [udp_trackers.network]
• Safe defaults when the block is omitted
• Rejection of the removed [core.net] layout
• Rejection of the removed flat ipv6_v6only field on both tracker types

Closes #1640 (v3 schema slice — runtime migration deferred to #1980)

[Copilot]

Pull request overview

This PR updates the configuration crate’s v3.0.0 schema to make network-related settings per tracker instance (HTTP and UDP), removing the global core.net layout in v3 while keeping v2 unchanged. This supports mixed deployments (e.g., some HTTP trackers behind a reverse proxy, others direct) and enforces a strict schema boundary via serde unknown-field rejection.

Changes:

• Introduces a v3 per-instance network: Network block (including external_ip, on_reverse_proxy, ipv6_v6only) on both HttpTracker and UdpTracker.
• Removes v3 Core.net and v3-only helper Configuration::get_ext_ip(), and adds tests to ensure removed v2 layouts are rejected in v3.
• Adds an ADR documenting the decision and updates EPIC/spec documentation and ADR index.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/configuration/src/v3_0_0/network.rs	Adds ipv6_v6only to Network and enforces strict v3 deserialization with deny_unknown_fields.
packages/configuration/src/v3_0_0/http_tracker.rs	Replaces flat networking fields with network: Network and rejects removed/unknown fields in v3.
packages/configuration/src/v3_0_0/udp_tracker.rs	Same per-instance network: Network change for UDP tracker config.
packages/configuration/src/v3_0_0/core.rs	Removes net: Network from v3 Core and rejects old [core.net] via deny_unknown_fields.
packages/configuration/src/v3_0_0/mod.rs	Updates docs/tests/defaults for the new per-tracker network block and adds v3 schema boundary rejection tests.
docs/adrs/20260721000000_make_network_configuration_per_tracker_instance.md	New ADR documenting the per-instance networking decision and explicit non-fallback v3 boundary.
docs/adrs/index.md	Registers the new ADR in the ADR index.
docs/issues/open/1640-1978-per-http-tracker-on-reverse-proxy-setting.md	Updates the spec to reflect the strict v3 boundary and deferred runtime migration to #1980.
docs/issues/open/1978-configuration-overhaul-epic.md	Updates EPIC progress/log to reflect the start of #1640 work and schema boundary clarifications.

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[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

[josecelano]

ACK f797ea7

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

[codecov]

Codecov Report

❌ Patch coverage is 97.70992% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.20%. Comparing base (3f03996) to head (f797ea7).

Files with missing lines	Patch %	Lines
packages/configuration/src/v3_0_0/mod.rs	97.50%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2014      +/-   ##
===========================================
+ Coverage    80.97%   81.20%   +0.22%     
===========================================
  Files          340      340              
  Lines        23901    24000      +99     
  Branches     23901    24000      +99     
===========================================
+ Hits         19355    19490     +135     
+ Misses        4236     4200      -36     
  Partials       310      310              

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