Add rudimentary Location return support for CompleteMultipartUpload

[daniel-sullivan]

Based on AWS documentation: https://docs.aws.amazon.com/AmazonS3/latest/API/API_CompleteMultipartUpload.html

A location URL should be returned for the newly created object. This implementation adds this field to the output.

Both PathBucket and HostBucket are supported.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 66.14%. Comparing base (edd0227) to head (58fe253). Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
gofakes3.go	83.33%	1 Missing and 1 partial :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #95 +/- ## ========================================== + Coverage 65.99% 66.14% +0.15% ========================================== Files 28 28 Lines 2697 2706 +9 ========================================== + Hits 1780 1790 +10 + Misses 651 649 -2 - Partials 266 267 +1 ```

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[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud