Update metadata parsing

model/src/main/kotlin/org/nixos/gradle2nix/DependencyCoordinates.kt

@@ -3,4 +3,6 @@ package org.nixos.gradle2nix.dependencygraph.model
 import kotlinx.serialization.Serializable
 
 @Serializable
-data class DependencyCoordinates(val group: String, val module: String, val version: String)
+data class DependencyCoordinates(val group: String, val module: String, val version: String) {
+    override fun toString(): String = "$group:$module:$version"
+}