minor STAC API updates

[tomkralidis]

Overview

Adds some minor STAC API updates

• applies RFC3339 functionality to dates
• adds numberMatched and numberReturned to STAC API collection responses
• ensures STAC item links have a rel property (rel=related is added if None)
• adds tests

Related Issue / Discussion

None

Additional Information

Sample code for testing:

import json

from pystac_client import Client
from pystac_client import ConformanceClasses

endpoint = 'http://localhost:8000/stac'

catalog = Client.open(endpoint)

print(catalog.id)

print(catalog.title)

print(catalog.description)

print(dir(ConformanceClasses))

print(catalog.conforms_to('ITEM_SEARCH'))
print(catalog.conforms_to('CORE'))

mysearch = catalog.search(collections=['metadata:main'], max_items=10)

print(f'{mysearch.matched()} items found')

mysearch = catalog.search(collections=['metadata:main'], bbox=[14.9,47.7,16.4,48.7], max_items=10)
print(f'{mysearch.matched()} items found')

items = mysearch.items()

for item in items:
    print(item.id)

Contributions and Licensing

(as per https://github.com/geopython/pycsw/blob/master/CONTRIBUTING.rst#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pycsw. I confirm that my contributions to pycsw will be compatible with the pycsw license guidelines at the time of contribution.
• I have already previously agreed to the pycsw Contributions and Licensing Guidelines