add DuplicateKeyException and ForeignKeyViolationException

[hurrba]

adds DuplicateKeyException and ForeignKeyViolationException

[isoos]

Thank you! I've added a note in the changelog, bumped the version, but would delay publishing just a bit: in case we have something more over the next days, I'd rather bundle it up to get more change in a version. However, if you feel strongly about it, let me know and I can publish it any time.

[isoos]

@hurrba:
Hm, I've just checked this page: https://www.postgresql.org/docs/current/errcodes-appendix.html
and the error code for 23505 is unique_violation. I think I will rename the exception to UniqueViolationException if you don't mind.

[hurrba]

ah, yes that probably a good idea

[isoos]

Published as 3.5.3.

[davidmartos96]

@isoos Could this PR implementation be reconsidered to be less breaking?

We have several instances where we handle PG errors as follows. I assume other people would have similar code, since 99% of the times the library throws ServerExceptions with all the fields.
On top of this error handling, we have other places which actually detect which constraintName failed, which is available in the ServerException class.
With this implementation those extra fields are not available.

Maybe the new exceptions could extend ServerException?

[isoos]

Maybe the new exceptions could extend ServerException?

That's a very good point, I'll fix it shortly.

[isoos]

Fixed the class hierarchy, published a new version, also retracted the previous one.