[Produce] Put explicit error when a mandatory field is not present in the dataset

[AlexisSouquiere]

Problem

When producing a message, an enrich phase is performed to be able to produce a compliant message. It adds for instance "field": null on union-nullable fields that are not given in the message. When a mandatory field is missing, the user get an error such as:

Produce failed due to the following error: java.lang.NullPointerException: Cannot invoke "java.util.List.forEach(java.util.function.Consumer)" because the return value of "java.util.Map.get(Object)" is null

User is blocked and can't know that a field is missing.

Suggestion

Add a clear message indicating that a field is missing like: Produce failed due to the following error: Mandotory field <field> is missing. Please check the schema to fix the dataset

Alternatives Considered

N/A

Additional Context

N/A