Object metadata parsing

[jonaustin09]

Describe the bug
When creating a new object with metadata, the action stores metadata keys first letter capitalized.

To Reproduce

aws --endpoint-url http://localhost:7070 s3api put-object --bucket my-bucket --key foo --metadata key=val,key1=val1

*Result

{
  "Key": "val",
  "Key1": "val1"
}

Expected behavior
It has to store all the keys as they are, without any string modifications. The resulting metadata of the above call, when getting the object has to be the following:

{
  "key": "val",
  "key1": "val1"
}