Add x-amz-server-side-encryption header for AES256 SSE without customer key

[85danf]

Problem

See #770

Solution

The code in this PR adds the x-amz-server-side-encryption header in cases where SSE is configured to be AES256 but not customer key was provided.

Does this solution apply anywhere else?

• yes
• no

If yes, where?

The following versions (and onwards) are affected, I'm not sure about this repo's patch strategy so I opened it on the latest branch.

• 10.5.6
• 10.4.8
• 10.3.10
• 10.2.14
• 10.1.15
• 10.0.26

Test Strategy

Built locally and tested on our environment.

Testing done:

• Unit tests
• Integration tests
• System tests
• Manual tests

Release Plan

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[subhashiyer9]

@85danf Thanks for the fix.
Can you rebase to the oldest affected branch 10.0.x and update the PR?