Refactored coordinate serialization

[aniketsinghrawat]

As we are performing json serialization on coordinates in get_coordinates() here

weather-tools/weather_mv/loader_pipeline/util.py

Line 214 in edd742d

to_json_serializable_type(v)

Indexing by dimension coordinate labels fails for coordinates that are serialized to types not index-able by xarray (eg datetime.timedelta is serialized to floats; so when timedelta is a coordinate, .loc[] fails as it gives type mis match error)

weather-tools/weather_mv/loader_pipeline/bq.py

Lines 213 to 215 in edd742d

	for it in coordinates:
	# Use those index values to select a Dataset containing one row of data.
	row_ds = data_ds.loc[it]

This is fixed by performing json serialization after the indexing is done.

[alxmrs]

LGTM, thank you!