Support whitespace in tag keys and values

[slackfan]

Is this a bug fix or adding new feature?

This PR adds a feature.

What is this PR about? / Why do we need it?

The current EFS Driver implementation does not support whitespace in tagging keys and values while the EFS API itself does support that.

The proposed implementation adds escaping support for the whitespace, allowing to configure the tags accordingly so the Driver implementation can handle it and causes fancy potentially undesirable tag values being written in case this is not known.

I chose to implement this via escape sequence. Namely a backslash as this was chosen recently via PR #1693

Existing behavior is mainly kept. The only difference I propose to implement is that empty tag values are supported. Before the changes this raised an error, after the changes a missing colon separator leads to an empty value.

What testing is done?

Additional unit tests have been added.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: slackfan / name: slackfan (26e4adb, 81fb26f)

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[k8s-ci-robot]

Hi @slackfan. Thanks for your PR.

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[slackfan]

Also, for I chose not to modify The Helm charts helper function https://github.com/kubernetes-sigs/aws-efs-csi-driver/blob/master/charts/aws-efs-csi-driver/templates/_helpers.tpl#L50 As changing it would break existing behavior (existing workarounds in place). If it makes sense to add automatic escaping there, let me know.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: samuhale, slackfan
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