Add docs

Signed-off-by: Per Goncalves da Silva <[email protected]>

docs/draft/howto/single-ownnamespace-install.md

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+## Description
+
+!!! note
+This feature is still in *alpha* the `SingleOwnNamespaceInstallSupport` feature-gate must be enabled to make use of it.
+See the instructions below on how to enable it.
+
+---
+
+A component of OLMv0's multi-tenancy feature is its support of four [*installModes*](https://olm.operatorframework.io/docs/advanced-tasks/operator-scoping-with-operatorgroups/#targetnamespaces-and-their-relationship-to-installmodes):
+for operator installation:
+
+ - *OwnNamespace*: If supported, the operator can be configured to watch for events in the namespace it is deployed in.
+ - *SingleNamespace*: If supported, the operator can be configured to watch for events in a single namespace that the operator is not deployed in.
+ - *MultiNamespace*: If supported, the operator can be configured to watch for events in more than one namespace.
+ - *AllNamespaces*: If supported, the operator can be configured to watch for events in all namespaces.
+
+OLMv1 will not attempt multi-tenancy (see [design decisions document](../../project/olmv1_design_decisions.md)) and will think of operators
+as globally installed, i.e. in OLMv0 parlance, as installed in *AllNamespaces* mode. However, there are operators that
+were intended only for the *SingleNamespace* and *OwnNamespace* install modes. In order to make these operators installable in v1 while they
+transition to the new model, v1 is adding support for these two new *installModes*. It should be noted that, in line with v1's no multi-tenancy policy,
+users will not be able to install the same operator multiple times, and that in future iterations of the registry bundle format will not
+include *installModes*.
+
+## Demos
+
+### SingleNamespace Install
+
+[![SingleNamespace Install Demo](https://asciinema.org/a/w1IW0xWi1S9cKQFb9jnR07mgh.svg)](https://asciinema.org/a/w1IW0xWi1S9cKQFb9jnR07mgh)
+
+### OwnNamespace Install
+
+[![OwnNamespace Install Demo](https://asciinema.org/a/Rxx6WUwAU016bXFDW74XLcM5i.svg)](https://asciinema.org/a/Rxx6WUwAU016bXFDW74XLcM5i)
+
+## Enabling the Feature-Gate
+
+!!! tip
+
+This guide assumes OLMv1 is already installed. If that is not the case,
+you can follow the [getting started](../../getting-started/olmv1_getting_started.md) guide to install OLMv1.
+
+---
+
+Patch the `operator-controller` `Deployment` adding `--feature-gates=SingleOwnNamespaceInstallSupport=true` to the
+controller container arguments:
+
+```terminal title="Enable SingleOwnNamespaceInstallSupport feature-gate"
+kubectl patch deployment -n olmv1-system operator-controller-controller-manager --type='json' -p='[{"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value": "--feature-gates=SingleOwnNamespaceInstallSupport=true"}]'
+```
+
+Wait for `Deployment` rollout:
+
+```terminal title="Wait for Deployment rollout"
+kubectl rollout status -n olmv1-system deployment/operator-controller-controller-manager
+```
+
+## Configuring the `ClusterExtension`
+
+A `ClusterExtension` can be configured to install bundle in `Single-` or `OwnNamespace` mode through the
+`olm.operatorframework.io/watch-namespace: <namespace>` annotation. The *installMode* is inferred in the following way:
+
+ - *AllNamespaces*: `<namespace>` is empty, or the annotation is not present
+ - *OwnNamespace*: `<namespace>` is the install namespace (i.e. `.spec.namespace`)
+ - *SingleNamespace*: `<namespace>` not the install namespace
+
+### Examples
+
+``` terminal title="SingleNamespace install mode example"
+kubectl apply -f - <<EOF
+apiVersion: olm.operatorframework.io/v1
+kind: ClusterExtension
+metadata:
+  name: argocd
+  annotations:
+    olm.operatorframework.io/watch-namespace: argocd-watch
+spec:
+  namespace: argocd
+  serviceAccount:
+    name: argocd-installer
+  source:
+    sourceType: Catalog
+    catalog:
+      packageName: argocd-operator
+      version: 0.2.1 # Update to version 0.2.1
+    EOF
+```
+
+``` terminal title="OwnNamespace install mode example"
+kubectl apply -f - <<EOF
+apiVersion: olm.operatorframework.io/v1
+kind: ClusterExtension
+metadata:
+  name: argocd
+  annotations:
+    olm.operatorframework.io/watch-namespace: argocd
+spec:
+  namespace: argocd
+  serviceAccount:
+    name: argocd-installer
+  source:
+    sourceType: Catalog
+    catalog:
+      packageName: argocd-operator
+      version: 0.2.1 # Update to version 0.2.1
+    EOF
+```