Minor fixes based on review

* added schema
* used declared_params
* fixed minor typos

doc/api/issue_links.md

@@ -48,7 +48,7 @@ Parameters:
     "web_url": "http://example.com/example/example/issues/14",
     "confidential": false,
     "weight": null,
-    "link_type": "relates_to",
+    "link_type": "relates_to"
   }
 ]
 ```

ee/lib/api/issue_links.rb

@@ -39,7 +39,7 @@ module API
         target_issue = find_project_issue(declared_params[:target_issue_iid],
                                           declared_params[:target_project_id])
 
-        create_params = { target_issuable: target_issue, link_type: params[:link_type] }
+        create_params = { target_issuable: target_issue, link_type: declared_params[:link_type] }
 
         result = ::IssueLinks::CreateService
                    .new(source_issue, current_user, create_params)

ee/spec/fixtures/api/schemas/public_api/v4/issue_link.json

+{
+  "type": "object",
+  "properties" : {
+     "source_issue": {
+       "allOf": [
+          { "$ref": "../../../../../../../spec/fixtures/api/schemas/public_api/v4/issue.json" }
+        ]
+     },
+     "target_issue": {
+       "allOf": [
+          { "$ref": "../../../../../../../spec/fixtures/api/schemas/public_api/v4/issue.json" }
+        ]
+     },
+     "link_type": {
+       "type": "string",
+       "enum": ["relates_to", "blocks", "is_blocked_by"]
+     }
+  },
+  "required" : [ "source_issue", "target_issue", "link_type" ]
+}

ee/spec/fixtures/api/schemas/public_api/v4/issue_links.json

+{
+  "type": "array",
+  "items": {
+    "type": "object",
+    "properties" : {
+      "$ref": "./issue_link.json"
+    }
+  }
+}

ee/spec/requests/api/issue_links_spec.rb

@@ -30,7 +30,7 @@ describe API::IssueLinks do
         expect(response).to have_gitlab_http_status(200)
         expect(json_response).to be_an Array
         expect(json_response.length).to eq(1)
-        expect(json_response.first).to include('iid', 'title', 'issue_link_id', 'link_type')
+        expect(response).to match_response_schema('public_api/v4/issue_links')
       end
     end
   end
@@ -119,14 +119,14 @@ describe API::IssueLinks do
           project.add_reporter(user)
         end
 
-        it 'returns 201' do
+        it 'returns 201 status and contains the expected link response' do
           post api("/projects/#{project.id}/issues/#{issue.iid}/links", user),
                params: { target_project_id: project.id, target_issue_iid: target_issue.iid, link_type: 'blocks' }
 
           expect_link_response(link_type: 'blocks')
         end
 
-        context 'when `issue_link_type` is disabled' do
+        context 'when `issue_link_types` is disabled' do
           before do
             stub_feature_flags(issue_link_types: false)
           end
@@ -148,7 +148,7 @@ describe API::IssueLinks do
 
         def expect_link_response(link_type: 'relates_to')
           expect(response).to have_gitlab_http_status(201)
-          expect(json_response).to include('source_issue', 'target_issue', 'link_type')
+          expect(response).to match_response_schema('public_api/v4/issue_link')
           expect(json_response['link_type']).to eq(link_type)
         end
       end
@@ -212,7 +212,7 @@ describe API::IssueLinks do
           delete api("/projects/#{project.id}/issues/#{issue.iid}/links/#{issue_link.id}", user)
 
           expect(response).to have_gitlab_http_status(200)
-          expect(json_response).to include('source_issue', 'target_issue', 'link_type')
+          expect(response).to match_response_schema('public_api/v4/issue_link')
         end
       end
     end