Give priority in Email to available subject message header

[Hooghof]

On development, the subject in the step can be overwritten by an available subject header. On next, the header is overwritten by the text in the subject field.
I expect that the subject is set by the subject message header.

Test case
Instance: next
Tenant: Regression Tests
Flow: Email_body_text

[brunovg]

The subject in the header takes precedence over subject option on the mail component, this is an Apache Camel inner logic.
Going to check if something changed on Apache Camel 4.21.0

[brunovg]

Yes, this was requested and implemented on 4.21.0:
https://issues.apache.org/jira/browse/CAMEL-23520