refactor: [#296] Phase 2: Create DockerComposeTopology Aggregate (P2.1, P2.2)

[josecelano]

Phase 2: Create DockerComposeTopology Aggregate

Issue: #296
Epic: #287 (Docker Compose Topology Domain Model Refactoring)

Summary

This PR implements Phase 2 of the Docker Compose Topology refactoring, introducing the DockerComposeTopology aggregate and establishing the single source of truth pattern for network derivation.

Changes

P2.1: Service Enum and Aggregate

• Service enum (src/domain/topology/service.rs): Type-safe service identification with 5 variants:

  • Tracker - Core BitTorrent tracker
  • MySQL - Database service
  • Prometheus - Metrics collection
  • Grafana - Visualization
  • Caddy - TLS proxy

• DockerComposeTopology aggregate (src/domain/topology/aggregate.rs):

  • Collects all ServiceTopology entries
  • Derives required_networks() from service configurations
  • Ensures deterministic ordering (alphabetical by name)
  • Enforces invariants: no orphan networks

• ServiceTopology struct: Links services to their network assignments

P2.2: Network Derivation in Context and Template

• NetworkDefinition type (context/network_definition.rs): Template-friendly network representation

• Context updates (context/mod.rs, context/builder.rs):

  • Added required_networks field to DockerComposeContext
  • Added derive_required_networks() method in builder
  • Networks collected from all enabled services, deduplicated, sorted

• Template update (docker-compose.yml.tera):

  • Replaced 4 conditional network blocks with single required_networks loop
  • Before: {%- if mysql %}\n database_network:\n driver: bridge\n{%- endif %}
  • After: {%- for net in required_networks %}\n {{ net.name }}:\n driver: {{ net.driver }}\n{%- endfor %}

Test Coverage

• 14 new tests for DockerComposeTopology aggregate
• 12 new tests for Service enum
• 5 new tests for NetworkDefinition
• 12 new tests for required_networks derivation in context
• All 389 unit tests pass
• All E2E tests pass (infrastructure lifecycle + deployment workflow)

Behavioral Equivalence

The generated docker-compose.yml output is functionally identical before and after this change. The only difference is implementation: networks are now derived from service configurations rather than duplicated in template conditionals.

Files Changed

File	Change
src/domain/topology/service.rs	NEW - Service enum
src/domain/topology/aggregate.rs	NEW - DockerComposeTopology aggregate
src/domain/topology/mod.rs	Modified - exports new types
src/domain/mod.rs	Modified - re-exports new types
context/network_definition.rs	NEW - NetworkDefinition type
context/mod.rs	Modified - required_networks field + tests
context/builder.rs	Modified - derive_required_networks()
docker-compose.yml.tera	Modified - uses required_networks loop

Progress Update

After this PR:

• ✅ ADR-01: Bind Mount Standardization (PR docs: [#288] add ADR for bind mount standardization #289)
• ✅ BUG-01: Remove invalid Grafana template branch (PR fix: [#290] remove dead Grafana-without-Prometheus template branch #291)
• ✅ Phase 0: Bind mounts (PR refactor: [#292] convert Docker named volumes to bind mounts #293)
• ✅ Phase 1: Network domain types (PR refactor: [#294] create Network domain type and migrate service configs #295)
• ✅ Phase 2: DockerComposeTopology aggregate (this PR)
• ⏳ Phase 3: Service volumes with bind mount type (next)
• ⏳ Phase 4: Integration in builder pipeline (final)

[josecelano]

ACK d51857b