BREAKING CHANGE: Setup refactor and code cleanup

This MR makes several major tweaks to the codebase. Primarily it adjusts
the setup steps for the application so that rather than providing just
the project ID in the `.gitlab.nvim` file, users can also provide a
vareity of other settings, such as auth_token, base_branch, and so
forth. This is to make the project more extensible in the future.

This MR also fixes a variety of issues with error handling in the code,
primarily in the request/response model between the Lua jobs and the
Golang server.

BREAKING CHANGE: Modifies `.gitlab.nvim` and setup steps

lua/gitlab/utils/init.lua

@@ -87,7 +87,9 @@ local base_invalid = function()
   local base = state.BASE_BRANCH
   local hasBaseBranch = feature_branch_exists(base)
   if not hasBaseBranch then
-    vim.notify('No base branch. If this is a Gitlab repository, please check your setup function!', vim.log.levels.ERROR)
+    vim.notify(
+      'Could not fetch feature branch. Please check that you have the correct base_branch value set in your .gitlab.nvim configuration file',
+      vim.log.levels.ERROR)
     return true
   end
 end
@@ -107,29 +109,6 @@ local add_comment_sign = function(line_number)
   vim.fn.sign_place(0, "piet", "piet", bufnr, { lnum = line_number })
 end
 
-local function is_gitlab_repo()
-  local current_dir = vim.fn.getcwd()
-
-  -- check if it contains a .git folder
-  local git_dir = current_dir .. "/.git"
-  if vim.fn.isdirectory(git_dir) == 0 then
-    return false
-  end
-
-  local git_cmd = 'git remote get-url origin'
-  local handle = io.popen(git_cmd)
-  local result = handle:read("*a")
-  handle:close()
-
-  -- check if the remote URL is a Gitlab URL
-  if string.match(result, "gitlab%.com") then
-    return true
-  else
-    return false
-  end
-end
-
-
 local function jump_to_file(filename, line_number)
   if line_number == nil then line_number = 1 end
   vim.api.nvim_command("wincmd l")
@@ -255,7 +234,6 @@ M.format_date = format_date
 M.add_comment_sign = add_comment_sign
 M.jump_to_file = jump_to_file
 M.find_value_by_id = find_value_by_id
-M.is_gitlab_repo = is_gitlab_repo
 M.darken_metadata = darken_metadata
 M.print_success = print_success
 M.print_error = print_error