Adding support for Hex keys

[zveinn]

Community Contribution License

All community contributions in this pull request are licensed to the project maintainers
under the terms of the Apache 2 license.
By creating this pull request I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 license.

Description

Due to the nature of S3 APIs and the way we declare encryption keys, we can not support encryption keys with the symbol = in them. This makes support for base64 encoding, which includes padding, impossible.

To provide an additional option to the RawBase64Encoding option, this PR adds support for Hex Encoding.

Motivation and Context

Most tools (openssl for example) generate base64 encoded keys with padding, so when they are used in scripts along with mc, they tend to fail. An alternative is to offer support for Hex encoding.

How to test this PR?

The functional test suite includes two tests for hex support.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here

[shtripat]

lgtm

[klauspost]

LGTM