Details of Helm charts with a slash in the chart-name cannot be displayed

[absoludity]

Describe the bug

When using Harbor as a helm repository for charts in a Harbor project, Harbor provides two possible URLs for the Helm index.yaml repository index:

• One endpoint which is for all charts on the harbor instance
• A project specific endpoint

The project specific endpoint works fine in Kubeapps, but if a user uses the single endpoint for all charts on the harbor instance, then the chart names are listed in the index.yaml file in the format <project-name>/<chart-name>.

These get sync'd to the Helm backend's postgresql database with IDs in the form <repo-name>/<project-name>/<chart-name>, whereas when retrieving the charts, Kubeapps looks for <repo-name>/<project-name>%2F<chart-name> (that is, the chart-name, from Kubeapps' perspective, should not contain any slashes). This was a decision made when the OCI repository support was added, as chart names include slashes in that case also, which are encoded so the single slash divides the kubeapps repo and the full chart name.

We should update the chart-sync for helm charts to ensure chart names with slashes are also encoded.

In the mean-time, the person who experienced this issue, is using the project-specific URL instead.

To Reproduce
Steps to reproduce the behavior:

1. Setup Harbor 2.7.0, create a project and add a helm chart
2. Add the instance-wide repo url to kubeapps as a Helm repository
3. View the catalog and click on the chart
4. An error is shown that Kubeapps is "unable to retrieve the chart: sql: no rows in result set".

If you check the api-server logs, you can verify Kubeapps is correctly looking for, for example, harbor-test/kubeapps%2Fnginx (ie. only a single slash between the repo and chart name, the the complete chart name being encoded), whereas if you check the database table you'll find the chart ID in the DB is harbor-test/kubeapps/nginx.

Expected behavior

The normal chart details are displayed.