Code generation fails when foreign key references a unique key that is not the primary key

[lukaseder]

There is a common misconception in jOOQ's code generation. In most RDBMS, a foreign key can reference any UNIQUE key, not only primary keys. Hence, the unique keys should be used instead of primary keys for referential generation

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Release 1.4.2 fixes code generation aborts. But check #69 for a more thorough problem solution