fix: allow space between checksums in header

[mcsimps2]

The current checksum logic only allowed checksum headers in the format crc32c=hash1,md5=hash2, but GCP may actually return them with a space in-between as crc32c=hash1, md5=hash2.

This means that checksums are not being verified correctly for any header response like the latter.

If you want an actual example of a response from GCP that demonstrates this, here's one:

{
   "X-GUploader-UploadID":"REDACTED",
   "Expires":"Tue, 08 Sep 2020 21:27:47 GMT",
   "Date":"Tue, 08 Sep 2020 21:27:47 GMT",
   "Cache-Control":"private, max-age=0",
   "Last-Modified":"Tue, 08 Sep 2020 21:27:47 GMT",
   "ETag":"REDACTED",
   "x-goog-generation": "REDACTED",
   "x-goog-metageneration":"1",
   "x-goog-stored-content-encoding":"identity",
   "x-goog-stored-content-length":"1043237",
   "Content-Type":"application/octet-stream",
   "x-goog-hash":"crc32c=t6zgHw==, md5=zH3E9XwJPGGra4vnT+aamQ==",
   "x-goog-storage-class":"STANDARD",
   "Accept-Ranges":"bytes",
   "Content-Length":"1043237",
   "Server":"UploadServer"
}

Resolves #169

[google-cla]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[google-cla]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[crwilcox]

Hi @mcsimps2 thank you for the contribution. Could I bother you to make a corresponding issue for this?

[mcsimps2]

@crwilcox It's mentioned in the summary at the bottom - it resolves #169. I should've made it more clear that was the issue of concern, sorry about that!

[crwilcox]

@mcsimps2 Cool, I just missed it :)

[crwilcox]

Tests are reporting failed for linting, which is not your pr. I can create a separate PR and clean that up.