⚠️ Major upgrade to Docs v6: the collaboration server is replaced by the new `yhub`
service, and existing documents have to be migrated to it, or they open EMPTY.

Before deploying, generate and insert two RSA keys:

  openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out jwt.pem
  openssl genpkey -algorithm RSA -pkeyopt rsa_keygen_bits:2048 -out yhub-jwt.pem
  abra app secret insert <app-name> jwt_pk v1 jwt.pem -f
  abra app secret insert <app-name> yhub_jwt_pk v1 yhub-jwt.pem -f

and add to your app config:

  SECRET_JWT_PK_VERSION=v1 # generate=false
  SECRET_YHUB_JWT_PK_VERSION=v1 # generate=false

`SECRET_COLLAB_SS_VERSION` and the `collab_ss` secret are no longer used.

After deploying (SOFT_MIGRATION is on by default), migrate all documents:

  abra app cmd <app-name> backend migrate_documents

Only then may you set SOFT_MIGRATION=false. See the README for details.