chore(datastore): update m-to-m integration tests models

Author: HuiSF

packages/amplify_datastore/example/lib/models/CpkPostTags.dart

@@ -191,9 +191,9 @@ class CpkPostTags extends Model {
 
     modelSchemaDefinition.indexes = [
       ModelIndex(
-          fields: const ["cpkManyToManyPostID"], name: "byCpkManyToManyPost"),
+          fields: const ["cpkManyToManyPostId"], name: "byCpkManyToManyPost"),
       ModelIndex(
-          fields: const ["cpkManyToManyTagID", "cpkManyToManyTaglabel"],
+          fields: const ["cpkManyToManyTagId", "cpkManyToManyTaglabel"],
           name: "byCpkManyToManyTag")
     ];
 
@@ -202,13 +202,13 @@ class CpkPostTags extends Model {
     modelSchemaDefinition.addField(ModelFieldDefinition.belongsTo(
         key: CpkPostTags.CPKMANYTOMANYPOST,
         isRequired: true,
-        targetNames: ["cpkManyToManyPostID"],
+        targetNames: ["cpkManyToManyPostId"],
         ofModelName: (CpkManyToManyPost).toString()));
 
     modelSchemaDefinition.addField(ModelFieldDefinition.belongsTo(
         key: CpkPostTags.CPKMANYTOMANYTAG,
         isRequired: true,
-        targetNames: ["cpkManyToManyTagID", "cpkManyToManyTaglabel"],
+        targetNames: ["cpkManyToManyTagId", "cpkManyToManyTaglabel"],
         ofModelName: (CpkManyToManyTag).toString()));
 
     modelSchemaDefinition.addField(ModelFieldDefinition.nonQueryField(

packages/amplify_datastore/example/lib/models/PostTags.dart

@@ -172,22 +172,22 @@ class PostTags extends Model {
     modelSchemaDefinition.pluralName = "PostTags";
 
     modelSchemaDefinition.indexes = [
-      ModelIndex(fields: const ["postID"], name: "byPost"),
-      ModelIndex(fields: const ["tagID"], name: "byTag")
+      ModelIndex(fields: const ["postId"], name: "byPost"),
+      ModelIndex(fields: const ["tagId"], name: "byTag")
     ];
 
     modelSchemaDefinition.addField(ModelFieldDefinition.id());
 
     modelSchemaDefinition.addField(ModelFieldDefinition.belongsTo(
         key: PostTags.POST,
         isRequired: true,
-        targetNames: ["postID"],
+        targetNames: ["postId"],
         ofModelName: (Post).toString()));
 
     modelSchemaDefinition.addField(ModelFieldDefinition.belongsTo(
         key: PostTags.TAG,
         isRequired: true,
-        targetNames: ["tagID"],
+        targetNames: ["tagId"],
         ofModelName: (Tag).toString()));
 
     modelSchemaDefinition.addField(ModelFieldDefinition.nonQueryField(