Issue #3457766 by narendraR, smustgrave: Add validation constraints to language.entity.*

language.entity.*:

  type: config_entity

  label: 'Language'

  constraints:

    FullyValidatable: ~

  mapping:

    id:

      type: string

      label: 'ID'

      constraints:

        NotBlank: []

        Regex:

          # @see \Drupal\Core\Language\LanguageInterface::VALID_LANGCODE_REGEX

          pattern: '/[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*/'

          message: 'This is not a valid language code.'

    label:

      type: required_label

      label: 'Label'

    direction:

      type: string

      label: 'Direction'

      constraints:

        # @see \Drupal\Core\Language\LanguageInterface::DIRECTION_LTR and

        # \Drupal\Core\Language\LanguageInterface::DIRECTION_RTL

        Choice: [ 'ltr', 'rtl' ]

    weight:

      type: weight

      label: 'Weight'