We need an OSSM 3 equivalent content of this page: https://docs.openshift.com/container-platform/4.16/service_mesh/v2x/ossm-create-mesh.html The content will be very different from OSSM 2, so this is high priority docs to include while in tech preview. Note that in OSSM 3, the ServiceMeshMember and ServiceMeshMember roll APIs are replaced by Istio's Discovery Selector feature.

The goal of this content is that the user's mesh is:

• Properly scoped (covering the desired set of namespaces and not interfering with other namespaces - or other meshes)
• Has the desired workloads included in the mesh with sidecars 

Topics may include:

• Introduction that describes how the Istio control plane (Istiod) and Istio is a cluster-level workload and resource, that without restriction will watch over (What does that mean?) the entire cluster. Discovery Selectors is an Istio feature that can be used to limit this to a specified set of namespaces based on labels. Discuss how individual workloads can be added to the mesh using labels.
• Using Discovery Selectors to Scope the service mesh to:
  • Include only a selection of namespaces (provide an example "Istio" config, similar to: https://istio.io/latest/blog/2021/discovery-selectors/)
  • Exclude a selection of namespaces
  • Verifying which namespaces are included
• Addition: Include a step by step example for scoping a service mesh to a single namespace for the control plane and data plane using Discovery Selectors 
• Sidecar injection has been split out into this issue: https://issues.redhat.com/browse/OSSM-8269

[Not part of engineering draft doc]Cross-Linking with Installation docs: We should add a note/callout in the installation instructions that by default OSSM is cluster-wide, and if you want to scope the mesh down to a set of namespaces, you will need to use Discovery Selectors. This is important, because in OSSM 2, the ServiceMeshMemberRoll provided this feature, but in OSSM 3, it is Discovery Selectors.  This relates to OSSM-8215.

Relevant upstream doc: https://istio.io/latest/docs/ops/configuration/mesh/configuration-scoping/. This contains additional scoping content (Sidecar, exportTo) that we may also want to include on this page - OR, include with "Scaling & Multi-tenant" doc, as tools for managing the mesh at scale. They are not needed for small meshes.