Extends dlango_jalali to supports database Extract functions

DabaseFunctions for django_jalali lib

# Adding support for Extracting date components for Jalali Date models
from django_jalali.db.models import jDateField, jDateTimeField
from django.db.models import (
    DateField, IntegerField,
    Transform,
)
from django.db.models.functions.datetime import TimezoneMixin


class jExtract(TimezoneMixin, Transform):
    lookup_name = None
    output_field = IntegerField()

    def __init__(self, expression, lookup_name=None, tzinfo=None, **extra):
        if self.lookup_name is None:
            self.lookup_name = lookup_name
        if self.lookup_name is None:
            raise ValueError('lookup_name must be provided')
        self.tzinfo = tzinfo
        super().__init__(expression, **extra)

    def as_sql(self, compiler, connection):
        sql, params = compiler.compile(self.lhs)
        lhs_output_field = self.lhs.output_field
        if isinstance(lhs_output_field, jDateTimeField):
            tzname = self.get_tzname()
            sql = connection.ops.datetime_extract_sql(self.lookup_name, sql, tzname)
        elif isinstance(lhs_output_field, jDateField):
            sql = connection.ops.date_extract_sql(self.lookup_name, sql)
        else:
            # resolve_expression has already validated the output_field so this
            # assert should never be hit.
            assert False, "Tried to jExtract from an invalid type."
        return sql, params

    def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
        copy = super().resolve_expression(query, allow_joins, reuse, summarize, for_save)
        field = copy.lhs.output_field
        if not isinstance(field, (jDateField, jDateTimeField)):
            raise ValueError(
                'jExtract input expression must be jDateField, jDateTimeField.'
            )
        # Passing dates to functions expecting datetimes is most likely a mistake.
        if type(field) == jDateField and copy.lookup_name in ('hour', 'minute', 'second'):
            raise ValueError(
                "Cannot extract time component '%s' from jDateField '%s'. " % (copy.lookup_name, field.name)
            )

        return copy


class jExtractYear(jExtract):

    lookup_name = 'year'


class jExtractMonth(jExtract):

    lookup_name = 'month'


class jExtractDay(jExtract):

    lookup_name = 'day'


class jExtractWeek(jExtract):
    """
    Return 1-52 or 53, based on ISO-8601, i.e., Monday is the first of the
    week.
    """

    lookup_name = 'week'


class jExtractWeekDay(jExtract):
    """
    Return Sunday=1 through Saturday=7.

    To replicate this in Python: (mydatetime.isoweekday() % 7) + 1
    """

    lookup_name = 'week_day'


class jExtractQuarter(jExtract):

    lookup_name = 'quarter'


DateField.register_lookup(jExtractYear)
DateField.register_lookup(jExtractMonth)
DateField.register_lookup(jExtractDay)
DateField.register_lookup(jExtractWeekDay)
DateField.register_lookup(jExtractWeek)
DateField.register_lookup(jExtractQuarter)