Simplify the introductory container installation docs (#1729)

It's a best practice to run Volto in seamless mode, where the API is served at the same domain with the /++api++ prefix. This avoids complications with browser cross-origin restrictions when the browser accesses the backend directly at a different domain.

So, we should show this best practice here. The current example sets RAZZLE_API_PATH, because the default is http://localhost:8080/Plone which does not work inside a container. But, setting RAZZLE_API_PATH also stops using the best practice of seamless mode. We can avoid this by setting RAZZLE_DEV_PROXY_API_PATH instead.

(Future improvement: make Volto recognize when it is running in a container, so that it can use http://host.docker.internal:8080/Plone as the default API path instead of localhost. Then it would not be necessary to set RAZZLE_DEV_PROXY_API_PATH here.)

Co-authored-by: David Glick <david@glicksoftware.com>

Author: stevepiercy

docs/install/containers/index.md

@@ -66,13 +66,13 @@ Docker Desktop includes all Docker tools.
 First start the Plone Backend, naming it `plone6-backend` and creating a site with its default configuration, using the following command.
 
 ```shell
-docker run --name plone6-backend -e SITE=Plone -e CORS_ALLOW_ORIGIN='*' -d -p 8080:8080 plone/plone-backend:{PLONE_BACKEND_MINOR_VERSION}
+docker run --name plone6-backend -e SITE=Plone -d -p 8080:8080 plone/plone-backend:{PLONE_BACKEND_MINOR_VERSION}
 ```
 
 Now start the Plone Frontend, linking it to the `plone6-backend`:
 
 ```shell
-docker run --name plone6-frontend --link plone6-backend:backend -e RAZZLE_API_PATH=http://localhost:8080/Plone -e RAZZLE_INTERNAL_API_PATH=http://backend:8080/Plone -d -p 3000:3000 plone/plone-frontend:latest
+docker run --name plone6-frontend --link plone6-backend:backend -e RAZZLE_DEV_PROXY_API_PATH=http://backend:8080/Plone -d -p 3000:3000 plone/plone-frontend:latest
 ```