Expose `release_links.link_type` via API

Part of https://gitlab.com/gitlab-org/gitlab/-/issues/207257

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/33154

changelogs/unreleased/207257-specify-asset-types-in-releases-2.yml

+---
+title: Expose `release_links.type` via API
+merge_request: 33154
+author:
+type: changed

lib/api/entities/releases/link.rb

@@ -9,6 +9,7 @@ module API
         expose :url
         expose :direct_asset_url
         expose :external?, as: :external
+        expose :link_type
 
         def direct_asset_url
           return object.url unless object.filepath

lib/api/release/links.rb

@@ -40,6 +40,7 @@ module API
               requires :name, type: String, desc: 'The name of the link'
               requires :url, type: String, desc: 'The URL of the link'
               optional :filepath, type: String, desc: 'The filepath of the link'
+              optional :link_type, type: String, desc: 'The link type'
             end
             post 'links' do
               authorize! :create_release, release
@@ -75,6 +76,7 @@ module API
                 optional :name, type: String, desc: 'The name of the link'
                 optional :url, type: String, desc: 'The URL of the link'
                 optional :filepath, type: String, desc: 'The filepath of the link'
+                optional :link_type, type: String, desc: 'The link type'
                 at_least_one_of :name, :url
               end
               put do

spec/factories/releases/link.rb

@@ -6,5 +6,6 @@ FactoryBot.define do
     sequence(:name) { |n| "release-18.#{n}.dmg" }
     sequence(:url) { |n| "https://example.com/scrambled-url/app-#{n}.zip" }
     sequence(:filepath) { |n| "/binaries/awesome-app-#{n}" }
+    link_type { 'other' }
   end
 end

spec/fixtures/api/schemas/release/link.json

@@ -7,7 +7,8 @@
     "filepath": { "type": "string" },
     "url": { "type": "string" },
     "direct_asset_url": { "type": "string" },
-    "external": { "type": "boolean" }
+    "external": { "type": "boolean" },
+    "link_type": { "type": "string" }
   },
   "additionalProperties": false
 }