Update how-to seciton about OKA preparation to fix image of KSU layers and...

osm oka-delete jenkins

```

#### OKA generation for helm charts:

#### OKA generation for helm charts

```bash

osm oka-generate jenkins --base-directory okas --profile-type app-profile --helm-repo-name bitnamicharts --helm-repo-url oci://registry-1.docker.io/bitnamicharts --helm-chart jenkins --version 13.4.20 --namespace jenkins

2. Overlays that allow customization of these manifests. They are changes relative to the original manifests.

3. Modifications to the overlays that OSM can make at instantiation time (KSU deployment).

```mermaid

block-beta

columns 3

  space blockArrowId<["&nbsp;&nbsp;&nbsp;"]>(down) space

  space A["Manifests"] space

  space B["Overlays"] space

  space C["OSM modifications"] space

  %% A --> B

  %% B --> C

```

![Layers contributing to a KSU](assets/layers-contributing-to-a-ksu.png)

Manifests and overlays can be encapsulated in a package called OKA. Examples of OKAs can be found [here](https://osm.etsi.org/gitlab/vnf-onboarding/osm-packages/-/tree/master/oka?ref_type=heads)

Please use the right path pointing to the folder where the manifests of your OKA are located (`./apps/jenkins/manifests` in this case).

For the moment, we will skip the meaning of the variable `${APPNAME}`.

For the moment, we will skip the meaning of variables such as `${APPNAME}` or `${TARGET_NS}`.

Then, we need to define in the kustomization the overlay patches (second layer) that will be applied to the manifests.

- Overlay patch.

  - It follows the mechanisms described [here](https://fluxcd.io/flux/components/kustomize/kustomizations/#patches)

  - They are added with the directive: `patches`.

  - Example:

  - Example from `apps/namespace` OKA:

    ```yaml

    patches:

            value: finalnamespace

    ```

  - Example from `apps/jenkins` OKA:

    ```yaml

    patches:

      - target:

          kind: HelmRelease

          version: v2beta1

          name: jenkins

          namespace: jenkins

        patch: |-

          - op: replace

            path: /metadata/name

            value: ${APPNAME}

          - op: replace

            path: /spec/chart/spec/sourceRef/namespace

            value: ${TARGET_NS}

          - op: replace

            path: /spec/targetNamespace

            value: ${TARGET_NS}

      - target:

          kind: HelmRepository

          version: v2beta1

          name: bitnamicharts

          namespace: jenkins

        patch: |-

          - op: replace

            path: /metadata/namespace

            value: ${TARGET_NS}

    ```

- Postbuilder: A simple parameterization mechanism that allows replacing values defined in the manifests. It can be compared to Helm values but is less powerful.

  - It follows the mechanisms described [here](https://fluxcd.io/flux/components/kustomize/kustomizations/#post-build-variable-substitution)

  - They are added with the directive `postbuild`.

  - Manifests should be properly updated to use the variables that will be substituted by the `postBuild` directive. For instance, the manifests for `apps/testacme` OKA [here](https://osm.etsi.org/gitlab/vnf-onboarding/osm-packages/-/tree/master/oka/apps/testacme/manifests?ref_type=heads) use the variables `${appname}`, `${target_ns}` and `${echo:message}`. 

  - Manifests should be properly updated to use the variables that will be substituted by the `postBuild` directive. For instance, the manifests for `apps/testacme` OKA [here](https://osm.etsi.org/gitlab/vnf-onboarding/osm-packages/-/tree/master/oka/apps/testacme/manifests?ref_type=heads) use the variables `${appname}`, `${target_ns}` and `${echo_message}`.

  - Example:

    ```yaml

osm oka-add jenkins ${OKA_FOLDER}/namespace --description namespace --profile-type app-profile

osm oka-add jenkins ${OKA_FOLDER}/jenkins --description jenkins --profile-type app-profile

osm oka-add testacme ${OKA_FOLDER}/testacme --description testacme --profile-type app-profile

osm ksu-create --ksu namespace --profile mydemo --profile-type app-profile --oka namespace

osm ksu-create --ksu namespace --profile mydemo --profile-type app-profile --oka namespace --params ${OKA_FOLDER}/jenkins-ns-params.yaml

osm ksu-create --ksu testacme --profile mydemo --profile-type app-profile --oka testacme --params ${OKA_FOLDER}/testacme-params.yaml

osm ksu-create --ksu jenkins --description "Jenkins" --profile mydemo --profile-type app-profile --oka jenkins --params ${OKA_FOLDER}/jenkins-params.yaml

```