Embeddable containing the affected column:
The exception itself is about missing column or naming strategy (which is another problem), but this bug refers to incorrect usage of "unique constraint", since the code never specifies unique=true, so it should be just a regular index. i.e. "Unable to create index" would be an accurate error message.
An additional issue (which may be another bug?) is that hibernate.ddl-auto is not set, so I'm wondering why would Hibernate want to create anything?