[patch] Allowing DatabaseWrapper to support extra kwargs as settings.DATABASE_OPTIONS

[ymasuda <ymasuda@…>]

It would be nice to support extra keyword arguments on backends.*.DatabaseWrapper to tweak backend-specific behaviour of connect().

For example, MySQLdb supports charset keyword argument that can be used to set-default-character-set as utf8.
Allowing extra keyword arguments works as follows:

1. specify {'charset': 'utf8'} on settings.DATABASE_OPTIONS (which defaults to empty dictionary)
2. settings.DATABASE_OPTIONS is passed to DatabaseWrapper as keyword arguments: (connection = backend.DatabaseWrapper(**settings.DATABASE_OPTIONS))
3. DatabaseWrapper.init() saves kwargs as self.options
4. on DatabaseWrapper.cursor(), which build connection as needed, passes self.options as extra keyword argument: self.connection = Database.connect(**kwargs)

Attached diff includes changes on django.conf.global_settings, django.db.init, and django.db.backends.*.base.
Please note that currently kwargs are just ignored on ado_mssql (that backend does not support extra kwargs).

[ymasuda <ymasuda@…>]

Diff to add settings.DATABASE_OPTIONS and kwargs on DatabaseWrapper

[Ludovico Magnocavallo]

Being able to pass an additional 'charset' argument to the MySQLdb connection is very important, as there are many occasions when the backend will raise the dreaded "Warning: Data truncated for column '...' at row ..." otherwise. Please commit this patch, or one of the others found in similar tickets.

[Jacob]

(In [4048]) Fixed #2866: Added DATABASE_OPTIONS setting which gets passed as extra kwargs to the backend's connect method. Thanks, ymasuda.