In lieu of #283, implement Stackdriver Canary Analysis for use in GKE.

As we are constantly upgrading Flagr server, the client SDKs may experience unexpected changes from the server side. The integration tests should better include these SDKs instead of just simple CURL tests.

Specifically, we want to cover

• https://github.com/checkr/jsflagr
• https://github.com/checkr/rbflagr
• https://github.com/checkr/pyflagr
• https://github.com/checkr/goflagr

Right now, when you archive a key, you can only see it if you manually search for it.

This can cause some key name conflict issues, or issues when trying to create a folder with the same name as an archived (bu not yet deleted key).

It would be ideal for there to be a way to see all archived keys at once, without the need to search for them in the search bar.

Documentation is not up to date

For example, supported datastores misses PGSQL
https://maif.github.io/izanami/manual/architecture/index.html

Please documentation freshness problems in this issue

Is your feature request related to a problem? Please describe.
Knative version used in examples (including platform setup is v0.20). New version of Knative (0.21) is out.

Describe the solution you'd like
Replace v0.20 with v0.21 in the docs