enhancement: Easier configuration of the postgres command

modules/postgresql/src/main/java/org/testcontainers/containers/PostgreSQLContainer.java

@@ -4,9 +4,14 @@
 import org.testcontainers.containers.wait.strategy.LogMessageWaitStrategy;
 import org.testcontainers.utility.DockerImageName;
 
+import lombok.NonNull;
+
 import java.time.Duration;
 import java.time.temporal.ChronoUnit;
+import java.util.Map;
+import java.util.HashMap;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 /**
  * Testcontainers implementation for PostgreSQL.
@@ -39,7 +44,7 @@ public class PostgreSQLContainer<SELF extends PostgreSQLContainer<SELF>> extends
 
     private String password = "test";
 
-    private static final String FSYNC_OFF_OPTION = "fsync=off";
+    private final Map<String, String> CONFIG_OPTIONS = new HashMap<>(Map.of("fsync", "off"));
 
     /**
      * @deprecated use {@link #PostgreSQLContainer(DockerImageName)} or {@link #PostgreSQLContainer(String)} instead
@@ -62,7 +67,6 @@ public PostgreSQLContainer(final DockerImageName dockerImageName) {
                 .withRegEx(".*database system is ready to accept connections.*\\s")
                 .withTimes(2)
                 .withStartupTimeout(Duration.of(60, ChronoUnit.SECONDS));
-        this.setCommand("postgres", "-c", FSYNC_OFF_OPTION);
 
         addExposedPort(POSTGRESQL_PORT);
     }
@@ -85,6 +89,35 @@ protected void configure() {
         addEnv("POSTGRES_DB", databaseName);
         addEnv("POSTGRES_USER", username);
         addEnv("POSTGRES_PASSWORD", password);
+
+        // If user never configured a command, and CONFIG_OPTIONS exist, then generate command
+        if (this.getContainerDef().getCommand().length == 0 && CONFIG_OPTIONS.size() > 0) {
+            this.setCommand("postgres -c " + CONFIG_OPTIONS.entrySet().stream().map(e -> e.getKey() + "=" + e.getValue()).collect(Collectors.joining(" -c ")));
+        }
+    }
+
+    /**
+     * Collects a set of configurations that will be set as a startup command of the PostgreSQL container.
+     * Note: configuration options will be ignored if a command is set using either withCommand() or setCommand()
+     * 
+     * <pre>
+     * For example:
+     *   postgresql.withConfigOption("max_prepared_transactions", "5").withConfigOption("log_destination", "'syslog'");
+     * 
+     * Will result in the startup command:
+     *   postgres -c max_prepared_transactions=5 -c log_destination='syslog'
+     * </pre>
+     * 
+     * @param key The configuration name
+     * @param value the configuration value
+     * @return self
+     */
+    public SELF withConfigOption(@NonNull String key, @NonNull String value) {
+        if(!key.matches("[a-zA-Z0-9_]")) {
+            throw new IllegalArgumentException("PostgreSQL configuration option with key: " + key + " is an invalid configuration string.");
+        }
+        CONFIG_OPTIONS.put(key, value);
+        return self();
     }
 
     @Override

modules/postgresql/src/test/java/org/testcontainers/junit/postgresql/SimplePostgreSQLTest.java

@@ -60,6 +60,25 @@ public void testUnsetCommand() throws SQLException {
         }
     }
 
+    @Test
+    public void testWithConfigOption() throws SQLException {
+        try (
+            PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>(PostgreSQLTestImages.POSTGRES_TEST_IMAGE)
+                .withConfigOption("max_connections", "42")
+        ) {
+            postgres.start();
+
+            ResultSet resultSet = performQuery(postgres, "SELECT current_setting('max_connections')");
+            String result = resultSet.getString(1);
+            assertThat(result).as("max_connections should be overriden").isEqualTo("42");
+
+            // Ensure default config
+            resultSet = performQuery(postgres, "SELECT current_setting('fsync')");
+            result = resultSet.getString(1);
+            assertThat(result).as("fsync should not overriden").isEqualTo("off");
+        }
+    }
+
     @Test
     public void testMissingInitScript() {
         try (