parse url for api docs

apps/block_scout_web/lib/block_scout_web/views/api_docs_view.ex

@@ -36,7 +36,9 @@ defmodule BlockScoutWeb.APIDocsView do
 
   def blockscout_url do
     if System.get_env("BLOCKSCOUT_HOST") do
-      "http://" <> System.get_env("BLOCKSCOUT_HOST")
+      %URI{host: host, scheme: scheme} = URI.parse(Endpoint.url())
+
+      scheme <> "://" <> host
     else
       Endpoint.url()
     end

apps/block_scout_web/test/block_scout_web/views/api_docs_view_test.exs

@@ -0,0 +1,14 @@
+defmodule BlockScoutWeb.ApiDocsViewTest do
+  use BlockScoutWeb.ConnCase, async: true
+
+  alias BlockScoutWeb.{APIDocsView, Endpoint}
+
+  describe "blockscout_url/0" do
+    test "returns url with scheme and host without port" do
+      System.put_env("BLOCKSCOUT_HOST", "localhost")
+
+      assert APIDocsView.blockscout_url() == "http://localhost"
+      assert Endpoint.url() == "http://localhost:4002"
+    end
+  end
+end