Flex Xuan

Results 4 issues of Flex Xuan

**What is the question**: Is this SDK still under development state? I want to know when the next version of this SDK will be release, because I see many changes...

**What this PR does / why we need it**: According to the newest spec, the before/after in sleep property should in ISO 8601 format. **Additional information (if needed):** > The...

**What would you like to be added**: Support authentication when loading external definitions **Why is this needed**: Since security is critical, so if I defined the AuthenticationDefinitions in an external...

**What happened**: After inject the serverless workflow, the application cannot run successfully **How to reproduce it**: Install the Serverlessworkflow.0.8.7 , then ![image](https://github.com/serverlessworkflow/sdk-net/assets/22612605/5f43e008-b8fe-45a4-893b-fed777811457)