Fix MR Selection, Go Code Refactor (#358)

refactor: Refactors the Go codebase into a more modular and idiomatic approach
fix: require selection of specific MR when there are multiple targets for a given source branch
feat: Allows for the passing of Gitlab's filter options when choosing an MR, improves MR selection
feat: API to choose an MR from a list based on the provided username's involvement as an assignee/reviewer/author

This is a #MINOR release

lua/gitlab/reviewer/init.lua

@@ -66,6 +66,14 @@ M.open = function()
     u.notify("This merge request has conflicts!", vim.log.levels.WARN)
   end
 
+  if state.INFO.state == "closed" then
+    u.notify(string.format("This MR was closed on %s", u.format_date(state.INFO.closed_at)), vim.log.levels.WARN)
+  end
+
+  if state.INFO.state == "merged" then
+    u.notify(string.format("This MR was merged on %s", u.format_date(state.INFO.merged_at)), vim.log.levels.WARN)
+  end
+
   if state.settings.discussion_diagnostic ~= nil or state.settings.discussion_sign ~= nil then
     u.notify(
       "Diagnostics are now configured as settings.discussion_signs, see :h gitlab.nvim.signs-and-diagnostics",