Update documentation about Knative serving encryption

[ReToCode]

Changes

• Update the encryption documentation to the latest discussion (the current docs are outdated)
• Add a diagrams to show the differences between the different parts of Knative Serving encryption

As we had several discussions in the past, this is an try to summarise and visualise how the different Serving encryption workstreams can align. Please note, this ONLY contains the work of the tracking issue #11906 and omits the mTLS stuff (for now). I'll also update the issues we have to hopefully get a more clear roadmap how we can achieve what is described in that document.

PTAL @davidhadas , @KauzClay , @dprotaso , @skonto , @nak3, @rhuss

[nak3]

LGTM.

I left a few comments. But they are just nit, it is alright without fix them.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.02% 🎉

Comparison is base (e937b62) 86.18% compared to head (049f8c6) 86.21%.
Report is 104 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14213      +/-   ##
==========================================
+ Coverage   86.18%   86.21%   +0.02%     
==========================================
  Files         199      195       -4     
  Lines       14811    14704     -107     
==========================================
- Hits        12765    12677      -88     
+ Misses       1741     1726      -15     
+ Partials      305      301       -4     

see 10 files with indirect coverage changes

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[krsna-m]

/approve
@KauzClay Could you review and give +1 if it looks good to you?

[krsna-m]

/hold
/unapprove

[krsna-m]

/lgtm

[ReToCode]

@dprotaso can this be merged? Some Approver magic is needed.

[rhuss]

Thanks @ReToCode , looks good to me. I think it reflects well the current status and also give an outlook to the parts that are still missing.

[ReToCode]

/assign @dprotaso

[dprotaso]

Looks good - though I notice the diagrams don't display text well in dark mode. (it's black on black)

[ReToCode]

Looks good - though I notice the diagrams don't display text well in dark mode. (it's black on black)

Good point, backgrounds were transparent, I changed it to white.

[ReToCode]

@dprotaso gentle ping

[dprotaso]

/lgtm
/approve

[knative-prow]

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