refactor: [#272] add MysqlServiceConfig for MySQL service network configuration

- Create MysqlServiceConfig in docker-compose context module
- Follow same pattern as CaddyServiceConfig (networks field only)
- Update docker-compose template to use mysql variable for network iteration
- Ensures consistency across all service configurations

Author: josecelano

src/infrastructure/templating/docker_compose/template/wrappers/docker_compose/context/builder.rs

@@ -7,6 +7,7 @@ use crate::domain::prometheus::PrometheusConfig;
 use super::caddy::CaddyServiceConfig;
 use super::database::{DatabaseConfig, MysqlSetupConfig, DRIVER_MYSQL, DRIVER_SQLITE};
 use super::grafana::GrafanaServiceConfig;
+use super::mysql::MysqlServiceConfig;
 use super::prometheus::PrometheusServiceConfig;
 use super::{DockerComposeContext, TrackerServiceConfig};
 
@@ -118,12 +119,20 @@ impl DockerComposeContextBuilder {
             None
         };
 
+        // Build MySQL service config if enabled
+        let mysql = if self.database.driver == DRIVER_MYSQL {
+            Some(MysqlServiceConfig::new())
+        } else {
+            None
+        };
+
         DockerComposeContext {
             database: self.database,
             tracker: self.tracker,
             prometheus,
             grafana,
             caddy,
+            mysql,
         }
     }
 }

src/infrastructure/templating/docker_compose/template/wrappers/docker_compose/context/mod.rs

@@ -11,6 +11,7 @@ mod builder;
 mod caddy;
 mod database;
 mod grafana;
+mod mysql;
 mod prometheus;
 mod tracker;
 
@@ -19,6 +20,7 @@ pub use builder::DockerComposeContextBuilder;
 pub use caddy::CaddyServiceConfig;
 pub use database::{DatabaseConfig, MysqlSetupConfig};
 pub use grafana::GrafanaServiceConfig;
+pub use mysql::MysqlServiceConfig;
 pub use prometheus::PrometheusServiceConfig;
 pub use tracker::{TrackerPorts, TrackerServiceConfig};
 
@@ -46,6 +48,12 @@ pub struct DockerComposeContext {
     /// This type only contains the docker-compose service definition data.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub caddy: Option<CaddyServiceConfig>,
+    /// `MySQL` service configuration (optional)
+    ///
+    /// Contains network configuration for the `MySQL` service.
+    /// This is separate from `MysqlSetupConfig` which contains credentials.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub mysql: Option<MysqlServiceConfig>,
 }
 
 impl DockerComposeContext {
@@ -124,6 +132,12 @@ impl DockerComposeContext {
     pub fn caddy(&self) -> Option<&CaddyServiceConfig> {
         self.caddy.as_ref()
     }
+
+    /// Get the `MySQL` service configuration if present
+    #[must_use]
+    pub fn mysql(&self) -> Option<&MysqlServiceConfig> {
+        self.mysql.as_ref()
+    }
 }
 
 #[cfg(test)]

src/infrastructure/templating/docker_compose/template/wrappers/docker_compose/context/mysql.rs

@@ -0,0 +1,91 @@
+//! `MySQL` service configuration for Docker Compose
+//!
+//! This module defines the `MySQL` service configuration for the docker-compose.yml template.
+//!
+//! ## Note on Configuration Separation
+//!
+//! There are two `MySQL`-related types in the docker-compose context:
+//!
+//! - `MysqlSetupConfig` (in database.rs): Contains credentials and initialization settings
+//!   for Docker Compose environment variables (root password, database name, user, etc.)
+//!
+//! - `MysqlServiceConfig` (this module): Contains service definition settings like networks,
+//!   following the same pattern as `CaddyServiceConfig`, `PrometheusServiceConfig`, etc.
+//!
+//! This separation keeps the pattern consistent across all services - each service
+//! has its own config type for networks and service-specific settings.
+
+use serde::Serialize;
+
+/// Network names used by the `MySQL` service
+const DATABASE_NETWORK: &str = "database_network";
+
+/// `MySQL` service configuration for Docker Compose
+///
+/// Contains configuration for the `MySQL` service definition in docker-compose.yml.
+/// This is intentionally minimal - the actual `MySQL` setup configuration (credentials)
+/// is in `MysqlSetupConfig`.
+///
+/// # Example
+///
+/// ```rust
+/// use torrust_tracker_deployer_lib::infrastructure::templating::docker_compose::template::wrappers::docker_compose::context::MysqlServiceConfig;
+///
+/// let mysql = MysqlServiceConfig::new();
+/// assert_eq!(mysql.networks, vec!["database_network"]);
+/// ```
+#[derive(Debug, Clone, Serialize, PartialEq)]
+pub struct MysqlServiceConfig {
+    /// Networks this service connects to
+    ///
+    /// `MySQL` only connects to `database_network` for isolation.
+    /// Only the tracker can access `MySQL` through this network.
+    pub networks: Vec<String>,
+}
+
+impl MysqlServiceConfig {
+    /// Creates a new `MysqlServiceConfig` with default networks
+    ///
+    /// `MySQL` connects to:
+    /// - `database_network`: For database access by the tracker
+    #[must_use]
+    pub fn new() -> Self {
+        Self {
+            networks: vec![DATABASE_NETWORK.to_string()],
+        }
+    }
+}
+
+impl Default for MysqlServiceConfig {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_should_create_mysql_config_with_database_network() {
+        let mysql = MysqlServiceConfig::new();
+
+        assert_eq!(mysql.networks, vec!["database_network"]);
+    }
+
+    #[test]
+    fn it_should_implement_default() {
+        let mysql = MysqlServiceConfig::default();
+
+        assert_eq!(mysql.networks, vec!["database_network"]);
+    }
+
+    #[test]
+    fn it_should_serialize_to_json() {
+        let mysql = MysqlServiceConfig::new();
+
+        let json = serde_json::to_value(&mysql).expect("serialization should succeed");
+
+        assert_eq!(json["networks"][0], "database_network");
+    }
+}

templates/docker-compose/docker-compose.yml.tera

@@ -64,7 +64,7 @@ services:
     #            Pinning to a stable release ensures predictable deployments and easier rollback.
     image: torrust/tracker:develop
     container_name: tracker
-{% if database.driver == "mysql" %}
+{% if mysql %}
     depends_on:
       mysql:
         condition: service_healthy
@@ -157,7 +157,7 @@ services:
 {% endif %}
 {% endif %}
 
-{% if database.driver == "mysql" %}
+{% if mysql %}
   mysql:
     <<: *defaults
     image: mysql:8.4
@@ -168,7 +168,9 @@ services:
       - MYSQL_USER=${MYSQL_USER}
       - MYSQL_PASSWORD=${MYSQL_PASSWORD}
     networks:
-      - database_network  # Only accessible by tracker
+{% for network in mysql.networks %}
+      - {{ network }}
+{% endfor %}
     ports:
       - "3306:3306"
     volumes:
@@ -210,7 +212,7 @@ services:
 # See Analysis: docs/analysis/security/docker-network-segmentation-analysis.md
 
 networks:
-{% if database.driver == "mysql" %}
+{% if mysql %}
   database_network:
     driver: bridge
 {% endif %}
@@ -227,9 +229,9 @@ networks:
     driver: bridge
 {% endif %}
 
-{% if database.driver == "mysql" or grafana or caddy %}
+{% if mysql or grafana or caddy %}
 volumes:
-{%- if database.driver == "mysql" %}
+{%- if mysql %}
   mysql_data:
     driver: local
 {%- endif %}