feat: add support for default_value with array of symbols

[demeyerthom]

This pull request adds support for array default values to the DefaultValue structure for Contentful content type fields. It updates validation logic, schema definitions, import/export methods, and tests to handle array default values alongside string and boolean types. This enables fields to have localized array defaults, such as {"en-US": ["green", "blue"]}.

Array default value support:

• The DefaultValue struct now includes an Array field, allowing array default values to be stored and processed. (internal/resources/contenttype/model.go, internal/resources/contenttype/model.goR43)
• The resource schema for content types has been updated to support array default values by locale, with validation logic extended to handle arrays. (internal/resources/contenttype/resource.go, [1]; internal/customvalidator/defaultvaluestructurevalidator.go, [2] [3] [4]

Import/export and utility enhancements:

• The Draft and HasContent methods for DefaultValue now correctly process array values, and the import logic in Field.Import can handle array default values from the SDK. (internal/resources/contenttype/model.go, [1] [2] [3]
• The getTypeOfMap utility function recognizes array types, improving type detection for default values. (internal/resources/contenttype/model.go, internal/resources/contenttype/model.goR653-R657)

Testing improvements:

• Comprehensive unit tests have been added for array default value handling, including validation, import, export, and type detection. (internal/resources/contenttype/model_test.go, internal/resources/contenttype/model_test.goR49-R361)
• Resource creation tests now verify correct handling and persistence of array default values for fields. (internal/resources/contenttype/resource_test.go, [1] [2] [3]
• Terraform test resource definitions updated to include a field with array default values. (internal/resources/contenttype/test_resources/create.tf, internal/resources/contenttype/test_resources/create.tfL32-R47)