Support the issuance of multiple verifiable credentials based on a directory attribute.

[mjspi]

API Reference: Credential Types | Issue Multiple Credentials to a User Based on a Directory Attribute

• Add multiple object, and its expression property to the CredentialType object.
• Add default property to the fields property object in the CredentialTypeMetaData object.

pingone_credential_type regression tests:

 TF_LOG=INFO TF_LOG_PATH=`pwd`/output.log TF_ACC=1 go test -v -timeout 240s  -run TestAccCredentialType_ github.com/pingidentity/terraform-provider-pingone/internal/service/credentials

=== RUN   TestAccCredentialType_RemovalDrift
=== PAUSE TestAccCredentialType_RemovalDrift
=== RUN   TestAccCredentialType_NewEnv
=== PAUSE TestAccCredentialType_NewEnv
=== RUN   TestAccCredentialType_Full
=== PAUSE TestAccCredentialType_Full
=== RUN   TestAccCredentialType_MetaData
=== PAUSE TestAccCredentialType_MetaData
=== RUN   TestAccCredentialType_CardDesignTemplate
=== PAUSE TestAccCredentialType_CardDesignTemplate
=== RUN   TestAccCredentialType_BadParameters
=== PAUSE TestAccCredentialType_BadParameters
=== CONT  TestAccCredentialType_RemovalDrift
=== CONT  TestAccCredentialType_MetaData
=== CONT  TestAccCredentialType_Full
=== CONT  TestAccCredentialType_BadParameters
=== CONT  TestAccCredentialType_CardDesignTemplate
=== CONT  TestAccCredentialType_NewEnv
--- PASS: TestAccCredentialType_MetaData (0.53s)
--- PASS: TestAccCredentialType_CardDesignTemplate (0.54s)
--- PASS: TestAccCredentialType_NewEnv (5.60s)
--- PASS: TestAccCredentialType_BadParameters (6.08s)
--- PASS: TestAccCredentialType_RemovalDrift (8.66s)
--- PASS: TestAccCredentialType_Full (32.16s)
PASS
ok      github.com/pingidentity/terraform-provider-pingone/internal/service/credentials 32.599s