Allow engine options to be set through the constructor like session options.

[keithjstone]

Package does not allow setting of custom engine options without monkey patching or inheriting the base class. This would allow options to be set and remembered prior to creating the engine in a blessed manner.

Our specific use-case is setting use_native_uuids to False on a postgres connection but I think this is more generally useful.

[ThiefMaster]

Probably not the best example for a unit test considering this one can be set through the flask config (SQLALCHEMY_ECHO)

[rsyring]

For what it's worth, I think the approach I documented in this comment is a better approach that this PR as it permits the engine options to be set in the Flask configuration.

The suggestion:

            options = {'convert_unicode': True}
            self._sa.apply_pool_defaults(self._app, options)
            self._sa.apply_driver_hacks(self._app, info, options)
            if echo:
                options['echo'] = echo

            # next two lines are new
            config_engine_opts = self._app.config.get('SQLALCHEMY_ENGINE_OPTS', {})
            options.update(config_engine_opts)

            self._engine = rv = sqlalchemy.create_engine(info, **options)

And it's only two lines difference.

[asteinlein]

👍 to having this in Flask configuration.

[rsyring]

Thank you for your contribution and sorry this took so long. I believe #684 will solve this use case.

[keithjstone]

Huge thanks for the fix! We had found a workaround locally so we could continue to use the published versions. Will be looking to update!