Support for "link_type" in issue links

[jmini]

According to https://docs.gitlab.com/ee/api/issue_links.html

Endpoint:

POST /projects/:id/issues/:issue_iid/links

Supports a link_type query parameter:

Type: string
Required: no
Description: The type of the relation (“relates_to”, “blocks”, “is_blocked_by”), defaults to “relates_to”).

So this would needs to be reflected here:

gitlab4j-api/src/main/java/org/gitlab4j/api/IssuesApi.java

Lines 847 to 871 in 075ce39

	/**
	* Creates a two-way relation between two issues. User must be allowed to update both issues in order to succeed.
	*
	* <p>NOTE: Only available in GitLab Starter, GitLab Bronze, and higher tiers.</p>
	*
	* <pre><code>GitLab Endpoint: POST /projects/:id/issues/:issue_iid/links</code></pre>
	*
	* @param projectIdOrPath the project in the form of an Long(ID), String(path), or Project instance
	* @param issueIid the internal ID of a project's issue
	* @param targetProjectIdOrPath the project in the form of an Long(ID), String(path), or Project instance of the target project
	* @param targetIssueIid the internal ID of a target project’s issue
	* @return an instance of IssueLink holding the link relationship
	* @throws GitLabApiException if any exception occurs
	*/
	public IssueLink createIssueLink(Object projectIdOrPath, Long issueIid,
	Object targetProjectIdOrPath, Long targetIssueIid) throws GitLabApiException {
	GitLabApiForm formData = new GitLabApiForm()
	.withParam("target_project_id", getProjectIdOrPath(targetProjectIdOrPath), true)
	.withParam("target_issue_iid", targetIssueIid, true);
	Response response = post(Response.Status.OK, formData.asMap(),
	"projects", getProjectIdOrPath(projectIdOrPath), "issues", issueIid, "links");
	return (response.readEntity(IssueLink.class));
	}

Maybe as enum?

And it needs to be present in IssueLink class (link_type attribute), when the response is parsed:

[
  {
    "id" : 84,
    "iid" : 14,
    "issue_link_id": 1,
    "project_id" : 4,
    "created_at" : "2016-01-07T12:44:33.959Z",
    "title" : "Issues with auth",
    "state" : "opened",
    "assignees" : [],
    "assignee" : null,
    "labels" : [
      "bug"
    ],
    "author" : {
      "name" : "Alexandra Bashirian",
      "avatar_url" : null,
      "state" : "active",
      "web_url" : "https://gitlab.example.com/eileen.lowe",
      "id" : 18,
      "username" : "eileen.lowe"
    },
    "description" : null,
    "updated_at" : "2016-01-07T12:44:33.959Z",
    "milestone" : null,
    "user_notes_count": 0,
    "due_date": null,
    "web_url": "http://example.com/example/example/issues/14",
    "confidential": false,
    "weight": null,
    "link_type": "relates_to",
    "link_created_at": "2016-01-07T12:44:33.959Z",
    "link_updated_at": "2016-01-07T12:44:33.959Z"
  }
]

---

Also the method reading the issue links GET /projects/:id/issues/:issue_iid/links should be reworked:

• getIssueLinks(Object projectIdOrPath, Long issueIid)
• getIssueLinks(Object projectIdOrPath, Long issueIid, int itemsPerPage)
• getIssueLinksStream(Object projectIdOrPath, Long issueIid)

But there I am not sure to understand why the return type is not from type IssueLink…