Incorrect header check when uploading an object with a retention configured using object lock

[Frank-Schmutz]

Hi ;)

The current version of moto requires the Content-Md5 header to be provided when uploading an object with a retention configured using object lock. However the AWS documentation specifies that the x-amz-sdk-checksum-algorithm header may be provided instead (AWS doc reference). I can confirm that the documentation is accurate after having performed a couple tests including the latter header instead of the content md5 one.
This issue is relevant since botocore does not compute and include the content md5 automatically since version 1.36.0, see changelog.

To fix this issue only a couple changes are required:
First in moto/s3/exceptions.py, the InvalidContentMD5 exception can be replaced by a new more descriptive one like:

class MissingUploadObjectWithObjectLockHeaders(S3ClientError):
    code = 400

    def __init__(self) -> None:
        super().__init__("MissingUploadObjectWithObjectLockHeaders", "Content-MD5 or x-amz-sdk-checksum-algorithm header required to upload an object with a retention period configured using Object Lock")

And in moto/s3/responses.py, in the _key_response_put method, the block that checks the headers can be updated to:

if lock_mode or lock_until or legal_hold == "ON":
    if not self.headers.get("Content-Md5") and not self.headers.get("x-amz-sdk-checksum-algorithm"):
        raise MissingUploadObjectWithObjectLockHeaders
    if not lock_enabled:
        raise LockNotEnabled

elif lock_enabled and bucket.has_default_lock:
    if not self.headers.get("Content-Md5") and not self.headers.get("x-amz-sdk-checksum-algorithm"):
        raise MissingUploadObjectWithObjectLockHeaders