Add resource keycloak_saml_script_protocol_mapper

[dullest]

This PR adds new resource keycloak_saml_script_protocol_mapper.

One issue I faced when implementing,

• OIDC script mapper requires configProperties name as script
• SAML script mapper requires configProperties name as Script

Because of this difference, we cannot reuse existing field scriptField

keycloak's OIDC mapper implementation

• https://github.com/keycloak/keycloak/blob/12.0.1/services/src/main/java/org/keycloak/protocol/oidc/mappers/ScriptBasedOIDCProtocolMapper.java#L55
• https://github.com/keycloak/keycloak/blob/12.0.1/services/src/main/java/org/keycloak/protocol/oidc/mappers/ScriptBasedOIDCProtocolMapper.java#L63

keycloak's SAML mapper implementation

• https://github.com/keycloak/keycloak/blob/12.0.1/server-spi/src/main/java/org/keycloak/provider/ProviderConfigProperty.java#L38
• https://github.com/keycloak/keycloak/blob/12.0.1/services/src/main/java/org/keycloak/protocol/saml/mappers/ScriptBasedMapper.java#L38

[shinji62]

@mrparkers Any chance we can get that merge please ?

[mrparkers]

LGTM - thanks for the PR! 🚀