refactor sigv4 out of rest catalog

[kevinjqliu]

iceberg-python/pyiceberg/catalog/rest/__init__.py

Lines 764 to 820 in 8055a60

	def _init_sigv4(self, session: Session) -> None:
	from urllib import parse
	import boto3
	from botocore.auth import SigV4Auth
	from botocore.awsrequest import AWSRequest
	from requests import PreparedRequest
	from requests.adapters import HTTPAdapter
	class SigV4Adapter(HTTPAdapter):
	def __init__(self, **properties: str):
	self._properties = properties
	max_retries = property_as_int(self._properties, SIGV4_MAX_RETRIES, SIGV4_MAX_RETRIES_DEFAULT)
	super().__init__(max_retries=max_retries)
	self._boto_session = boto3.Session(
	profile_name=get_first_property_value(self._properties, AWS_PROFILE_NAME),
	region_name=get_first_property_value(self._properties, AWS_REGION),
	botocore_session=self._properties.get(BOTOCORE_SESSION),
	aws_access_key_id=get_first_property_value(self._properties, AWS_ACCESS_KEY_ID),
	aws_secret_access_key=get_first_property_value(self._properties, AWS_SECRET_ACCESS_KEY),
	aws_session_token=get_first_property_value(self._properties, AWS_SESSION_TOKEN),
	)
	def add_headers(self, request: PreparedRequest, **kwargs: Any) -> None: # pylint: disable=W0613
	credentials = self._boto_session.get_credentials().get_frozen_credentials()
	region = self._properties.get(SIGV4_REGION, self._boto_session.region_name)
	service = self._properties.get(SIGV4_SERVICE, "execute-api")
	url = str(request.url).split("?")[0]
	query = str(parse.urlsplit(request.url).query)
	params = dict(parse.parse_qsl(query))
	# remove the connection header as it will be updated after signing
	if "connection" in request.headers:
	del request.headers["connection"]
	# For empty bodies, explicitly set the content hash header to the SHA256 of an empty string
	if not request.body:
	request.headers["x-amz-content-sha256"] = EMPTY_BODY_SHA256
	aws_request = AWSRequest(
	method=request.method, url=url, params=params, data=request.body, headers=dict(request.headers)
	)
	SigV4Auth(credentials, service, region).add_auth(aws_request)
	original_header = request.headers
	signed_headers = aws_request.headers
	relocated_headers = {}
	# relocate headers if there is a conflict with signed headers
	for header, value in original_header.items():
	if header in signed_headers and signed_headers[header] != value:
	relocated_headers[f"Original-{header}"] = value
	request.headers.update(relocated_headers)
	request.headers.update(signed_headers)
	session.mount(self.uri, SigV4Adapter(**self.properties))

into new file pyiceberg/catalog/rest/sigv4.py

and generally improve sigv4 implementation

• align on retry behavior (Retry Behavior for SigV4Adapter in REST Catalog #3008)
• fix request signing (fix: sigv4 auth to use base64-encoded content sha256 and custom canonical request #3120)

[adamdavis99]

Hi @kevinjqliu I'd like to take this on.
If I understood correctly, I need to extract _init_sigv4 and the nested SigV4Adapter into a new pyiceberg/catalog/rest/sigv4.py, keeping behavior identical and existing tests green, is that apt ?