Add id fluent setter to Entity.

[mshima]

Currently we are not generating fluent id setter.

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[murdos]

I think the reason was that we're not supposed to manually set the id of an entity.

[mshima]

I think the reason was that we're not supposed to manually set the id of an entity.

I think so, but for specific use cases this can be useful.
Eg: foo.bar(new bar().id(barId));.

For completeness I think it is better to include.