Refactor error classes

All runner errors are now in a single file. The not found error
has been splitted into an error for runner not found and for
environment not found.

app/errors/runner/error.rb

@@ -1,3 +1,21 @@
 # frozen_string_literal: true
 
-class Runner::Error < ApplicationError; end
+class Runner
+  class Error < ApplicationError
+    class BadRequest < Error; end
+
+    class EnvironmentNotFound < Error; end
+
+    class ExecutionTimeout < Error; end
+
+    class InternalServerError < Error; end
+
+    class NotAvailable < Error; end
+
+    class Unauthorized < Error; end
+
+    class RunnerNotFound < Error; end
+
+    class Unknown < Error; end
+  end
+end

app/errors/runner/error/bad_request.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::BadRequest < Runner::Error; end

app/errors/runner/error/execution_timeout.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::ExecutionTimeout < Runner::Error; end

app/errors/runner/error/internal_server_error.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::InternalServerError < Runner::Error; end

app/errors/runner/error/not_available.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::NotAvailable < Runner::Error; end

app/errors/runner/error/not_found.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::NotFound < Runner::Error; end

app/errors/runner/error/unauthorized.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::Unauthorized < Runner::Error; end

app/errors/runner/error/unknown.rb

@@ -1,3 +0,0 @@
-# frozen_string_literal: true
-
-class Runner::Error::Unknown < Runner::Error; end