Previously we were wrongly adding `?` as part
of the resource name, add a test case to check
if this is handled properly.
Thanks to @kannappanr for reproducing this.
Without this change presigned URL generated with following
command would fail with signature mismatch.
```
aws s3 presign s3://testbucket/functional-tests.sh
```
Values of canonicalized query resources should be unescaped before calculating
the signature. This bug is not noticed before because partNumber and uploadID
values in Minio doesn't have characters that need to be escaped.
This change is cleanup of the postPolicyHandler code
primarily to address the flow and also converting
certain critical parts into self contained functions.
Encode the path of the passed presigned url before calculating the signature. This fixes
presigning objects whose names contain characters that are found encoded in urls.
A client sends escaped characters in values of some query parameters in a presign url.
This commit properly unescapes queires to fix signature calculation.
Harshavardhana