Extending SANs DNS entries

[ctyano]

Description

This Pull Requests adds capability to set additional Subjct Alternative Names DNS field to the identity certificates issued by SIA.
Currently, the implementation restricts to have only certain syntaxes in SANs DNS and this restriction is limiting the use of the identity certificates for server certificate purposes.
This enhancement will bring more flexibility to add SANs DNS that matches their actual DNS domains.
For the security perspective it is recommended to always verify the SANs DNS in CSR by the instance identity provider.

Assignees

• Assignees is set

Type of changes

• Apply one or more labels of the following that fits:
  • enhancement: New Feature

Flags

• Breaks backward compatibility
• Requires a documentation update
• Has untestable code

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Checklist

• Followed the guidelines in the CONTRIBUTING document
• Added prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip] in the PR title if necessary
• Tested and linted the code
• Commented the code
• Made corresponding changes to the documentation

Checklist for maintainer

• Use Squash and merge
• Double-confirm the merge message has prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip]
• Delete the branch after merge

[mlajkim]

please modify this too: https://github.com/AthenZ/k8s-athenz-sia/blob/main/athenz-sia.env

[mlajkim]

• Please write the description in a simple manner

[mlajkim]

simple review.

[y-myajima]

LGTM