fix(link-modules): Fix link module initialization (#4990)

**What**
Add a new configuration on the relationship to specify if the relation is consumed from an internal service (from medusa core). In that case do not check if the service is part of the loaded modules

packages/link-modules/src/initialize/index.ts

@@ -90,8 +90,10 @@ export const initialize = async (
         continue
       }
     } else if (
-      !modulesLoadedKeys.includes(primary.serviceName) ||
-      !modulesLoadedKeys.includes(foreign.serviceName)
+      (!primary.isInternalService &&
+        !modulesLoadedKeys.includes(primary.serviceName)) ||
+      (!foreign.isInternalService &&
+        !modulesLoadedKeys.includes(foreign.serviceName))
     ) {
       continue
     }
@@ -176,8 +178,10 @@ export async function runMigrations(
     allLinks.add(serviceKey)
 
     if (
-      !modulesLoadedKeys.includes(primary.serviceName) ||
-      !modulesLoadedKeys.includes(foreign.serviceName)
+      (!primary.isInternalService &&
+        !modulesLoadedKeys.includes(primary.serviceName)) ||
+      (!foreign.isInternalService &&
+        !modulesLoadedKeys.includes(foreign.serviceName))
     ) {
       continue
     }