Introduced 'key' field on TaxRate

We introduced the key field on TaxRate and TaxRateDraft. This ensures a consistent experience when working with external identifiers across different entity types in Composable Commerce.

Changes:

• [API] Added the key field to TaxRate and TaxRateDraft.
• [API] Added the taxRateKey field to Remove TaxRate and Replace TaxRate update actions.
• [API] Changed the taxRateId field to be optional on Remove TaxRate and Replace TaxRate update actions.
• [GraphQL API] Changed the TaxRate type:
  • Added the key field to the TaxRate type.
• [GraphQL API] Changed the TaxRateInput type:
  • Input field key was added to TaxRateInput type
• [GraphQL API] Changed the TaxRateDraft type:
  • Input field key was added to TaxRateDraft type
• [GraphQL API] Changed the TaxCategoryRemoveTaxRate type:
  • Input field taxRateKey was added to TaxCategoryRemoveTaxRate type
  • TaxCategoryRemoveTaxRate.taxRateId input field type changed from String! to String
• [GraphQL API] Changed the TaxCategoryReplaceTaxRate type:
  • TaxCategoryReplaceTaxRate.taxRateId input field type changed from String! to String
  • Input field taxRateKey was added to TaxCategoryReplaceTaxRate type

The following changes were introduced in terms of GraphQL SDL:

extend type TaxRate {
  key: String
}

extend input TaxCategoryRemoveTaxRate {
  taxRateKey: String
}

extend input TaxRateInput {
  key: String
}

extend input TaxRateDraft {
  key: String
}

extend input TaxCategoryReplaceTaxRate {
  taxRateKey: String
}