[UK Toolkit] DCR request object JTI claim format validation

[aka4rKO]

Currently there is no format validation for the JTI claim in the DCR request object. According to the UK OB spec the JTI has to be:

1. A unique identifier for the JWT.
2. The value must be a UUIDv4 GUID.

This issue was created to track the implementation of 2. above.

ob-internal: https://github.com/wso2-enterprise/wso2-ob-internal/issues/1253