feat: enable secret types

[dwa012-zmi]

The original code assume that all synced secrets would be Opaque.
This change allows the user to add the correct key to the SyncedSecret to set the SecretType

[codecov]

Codecov Report

Merging #50 into master will increase coverage by 0.4%.
The diff coverage is 100.0%.

@@           Coverage Diff            @@
##           master     #50     +/-   ##
========================================
+ Coverage    59.3%   59.6%   +0.4%     
========================================
  Files           8       8             
  Lines         368     371      +3     
========================================
+ Hits          218     221      +3     
  Misses        119     119             
  Partials       31      31             

Impacted Files	Coverage Δ
pkg/k8ssecret/secret.go	80.7% <100.0%> (+0.7%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 720c4b1...64a7cfc. Read the comment docs.

[argvk]

Hey there,

Thanks a lot for the PR, I think this feature make sense. I've left a few comments requesting clarification.

[yannh]

Hi there 👋 and thanks a lot for the contribution, seems interesting! Wondering: should we do some value validation? It seems the list of valid values is pretty small: https://github.com/kubernetes/community/blob/master/contributors/design-proposals/auth/secrets.md#secret-api-resource ? Or can there be more values to this?