Add Epic information to Issue API

When using the Issue API, the Epic information is not available.

For example, the issue https://gitlab.com/gitlab-org/gitlab-ee/issues/10200 is assigned to the Epic &189 (closed), but when it is returned by the API there is no epic information as shown below:

{
                      "id" => 18793865,
                     "iid" => 10200,
              "project_id" => 278964,
                   "title" => "Geo edge case for deduplication: what happens when the source project is deleted right after a project gets forked?",
             "description" => "In the situation where a source project is deleted right after the project gets forked, by the time the Secondary tries to create the pool the source project will no longer exist and it will fail.\n\nwhat should we do in this situation?\n\n1. we could just let it fail\n2. we could, as a fallback clone the pool repository.\n    - but if we do this, why not just clone the pool repository when we do every repository sync?",
                   "state" => "opened",
              "created_at" => "2019-03-05T01:17:49.607Z",
              "updated_at" => "2019-03-06T22:51:30.766Z",
               "closed_at" => nil,
               "closed_by" => nil,
                  "labels" => [
        [0] "Accepting merge requests",
        [1] "Geo",
        [2] "Geo Replication/Sync",
        [3] "Gitaly",
        [4] "auto updated",
        [5] "git object deduplication"
    ],
               "milestone" => {
                 "id" => 693518,
                "iid" => 33,
           "group_id" => 9970,
              "title" => "12.0",
        "description" => "",
              "state" => "active",
         "created_at" => "2018-10-30T16:47:37.975Z",
         "updated_at" => "2019-01-16T19:49:11.208Z",
           "due_date" => "2019-06-22",
         "start_date" => "2019-05-08",
            "web_url" => "https://gitlab.com/groups/gitlab-org/-/milestones/33"
    },
               "assignees" => [],
                  "author" => {
                "id" => 668120,
              "name" => "John Cai",
          "username" => "johncai",
             "state" => "active",
        "avatar_url" => "https://assets.gitlab-static.net/uploads/-/system/user/avatar/668120/avatar.png",
           "web_url" => "https://gitlab.com/johncai"
    },
                "assignee" => nil,
        "user_notes_count" => 1,
    "merge_requests_count" => 0,
                 "upvotes" => 0,
               "downvotes" => 0,
                "due_date" => nil,
            "confidential" => false,
       "discussion_locked" => nil,
                 "web_url" => "https://gitlab.com/gitlab-org/gitlab-ee/issues/10200",
              "time_stats" => {
                 "time_estimate" => 0,
              "total_time_spent" => 0,
           "human_time_estimate" => nil,
        "human_total_time_spent" => nil
    },
                  "weight" => nil
}

Please could any Epic information be added to this response.