stac reader

[geospatial-jeff]

Closes #69

This PR adds a CompositeReader which allows performing the same operation over multiple COGReader instances via MapReduce. Composite readers implement the same interface as a normal reader (enforced through the ReaderMixin class). Also add the STACReader which extends CompositeReader.

The caller can easily implement their own filter/map/reduce functions, for example calculating ndvi from an naip stac item:

import asyncio
import os

os.environ['AWS_REQUEST_PAYER'] = "requester"

from aiocogeo.stac import STACReader
from stac_pydantic.shared import MimeTypes

def ndvi(arr):
    arr = arr[0]
    return (arr[3] - arr[1]) / (arr[3] + arr[1])

async def main():
    async with STACReader(
        filepath="http://stac.arturo.ai/collections/naip/items/m_3311717_nw_11_060_20180723",
        include_types={MimeTypes.cog}, # Only try to read COG types
        filter=lambda a: a.asset.name == "analytic_cog" # Filter for the asset with NIR band
    ) as reader:
        val = await reader.point(
            x=412382.1,
            y=3731494.7,
            reducer=ndvi
        )
        print(val)


asyncio.run(main())

>>> 0.35686275

[codecov-commenter]

Codecov Report

Merging #70 into master will decrease coverage by 3.22%.
The diff coverage is 73.78%.

@@            Coverage Diff             @@
##           master      #70      +/-   ##
==========================================
- Coverage   94.69%   91.46%   -3.23%     
==========================================
  Files          12       13       +1     
  Lines         886     1043     +157     
==========================================
+ Hits          839      954     +115     
- Misses         47       89      +42     

Impacted Files	Coverage Δ
aiocogeo/filesystems.py	82.69% <35.13%> (-10.38%)	⬇️
aiocogeo/tiler.py	80.73% <70.27%> (-5.94%)	⬇️
aiocogeo/cog.py	94.25% <85.18%> (-3.20%)	⬇️
aiocogeo/errors.py	100.00% <100.00%> (ø)
aiocogeo/stac.py	100.00% <100.00%> (ø)
aiocogeo/partial_reads.py	96.00% <0.00%> (+0.57%)	⬆️

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