Lesser Namespace#name validations

Since we use `Namespace#path` to build routes and URLs we can lessen
the restrictions on `Namespace#name` so it can accomodate a user's name.

app/models/namespace.rb

@@ -41,8 +41,7 @@ class Namespace < ApplicationRecord
   validates :owner, presence: true, unless: ->(n) { n.type == "Group" }
   validates :name,
     presence: true,
-    length: { maximum: 255 },
-    namespace_name: true
+    length: { maximum: 255 }
   validates :description, length: { maximum: 255 }
   validates :path,

app/validators/namespace_name_validator.rb

-# frozen_string_literal: true
-
-# NamespaceNameValidator
-#
-# Custom validator for GitLab namespace name strings.
-class NamespaceNameValidator < ActiveModel::EachValidator
-  def validate_each(record, attribute, value)
-    unless value =~ Gitlab::Regex.namespace_name_regex
-      record.errors.add(attribute, Gitlab::Regex.namespace_name_regex_message)
-    end
-  end
-end

lib/gitlab/regex.rb

@@ -4,14 +4,6 @@ module Gitlab
   module Regex
     extend self
-    def namespace_name_regex
-      @namespace_name_regex ||= /\A[\p{Alnum}\p{Pd}_\. ]*\z/.freeze
-    end
-
-    def namespace_name_regex_message
-      "can contain only letters, digits, '_', '.', dash and space."
-    end
-
     def project_name_regex
       @project_name_regex ||= /\A[\p{Alnum}\u{00A9}-\u{1f9c0}_][\p{Alnum}\p{Pd}\u{00A9}-\u{1f9c0}_\. ]*\z/.freeze
     end