Return correct error when creating a bucket with empty CreateBucketConfiguration

[dawngerpony]

Problem

1. See problem described in create_bucket should fail with CreateBucketConfiguration={} #2210.
2. One of the other S3 tests (test_streaming_upload_from_file_to_presigned_url) is failing on my machine due to the lack of a region. See test_streaming_upload_from_file_to_presigned_url fails #3080 for more information.
3. Some of the contributor documentation is a little sparse for newbies.

Changes

This PR:

• updates the contributor documentation
• fixes the failing S3 test by providing a region
• adds a test for empty CreateBucketConfiguration
• returns the correct exception when presented with an empty CreateBucketConfiguration

Notes

• 🙏 This is my first PR against this codebase, please be gentle!
• ℹ️ I'm using this as practice because I want to implement Application Autoscaling (Application Autoscaling service #1931).
• ❓ I'm not sure why test_streaming_upload_from_file_to_presigned_url is failing, it was passing yesterday.

Fixes #2210, fixes #3080

[coveralls]

Coverage increased (+0.002%) to 94.393% when pulling f78239f on dawngerpony:fix/2210-s3-empty-createbucketconfiguration into 6305f70 on spulec:master.

[bblommers]

Hi @dawngerpony, this looks good to me. Thanks for your PR, and welcome to Moto!

[bblommers]

Let me know if you need any help with the Application Autoscaling btw.

If you want an idea on how to get started with a completely new service, have a look at this PR: #2957 . It's a very clean implementation of the another new service (Managed Blockchain) that was introduced recently, and should be a good starting point.

[dawngerpony]

Thank you for the lovely welcome, @bblommers - I'm glad my PR looked good to you! 😄 Also thank you for the link to the PR, I'll use it as a template when mocking Application Auto Scaling.

[spulec]

Welcome to the team!