fix: product module joiner config (#8170)

* fix: product module joiner config

* fix aliases

* revert package.json

* add js doc

packages/core/utils/src/modules-sdk/define-link.ts

@@ -1,5 +1,5 @@
 import { LinkModulesExtraFields, ModuleJoinerConfig } from "@medusajs/types"
-import { isObject, pluralize, toPascalCase } from "../common"
+import { camelToSnakeCase, isObject, pluralize, toPascalCase } from "../common"
 import { composeLinkName } from "../link"
 
 export const DefineLinkSymbol = Symbol.for("DefineLink")
@@ -74,7 +74,7 @@ function prepareServiceConfig(input: DefineLinkInputSource) {
 
     serviceConfig = {
       key: source.linkable,
-      alias: source.field,
+      alias: camelToSnakeCase(source.field),
       primaryKey: source.primaryKey,
       isList: false,
       deleteCascade: false,
@@ -87,7 +87,7 @@ function prepareServiceConfig(input: DefineLinkInputSource) {
 
     serviceConfig = {
       key: source.linkable,
-      alias: source.field,
+      alias: camelToSnakeCase(source.field),
       primaryKey: source.primaryKey,
       isList: input.isList ?? false,
       deleteCascade: input.deleteCascade ?? false,
@@ -106,6 +106,14 @@ function prepareServiceConfig(input: DefineLinkInputSource) {
   return serviceConfig
 }
 
+/**
+ * Generate a ModuleJoinerConfig for the link definition on the fly.
+ * All naming, aliases etc are following our conventional naming.
+ *
+ * @param leftService
+ * @param rightService
+ * @param linkServiceOptions
+ */
 export function defineLink(
   leftService: DefineLinkInputSource,
   rightService: DefineLinkInputSource,