Issue #8113 : Document Hop Web Docker persistence and upgrades (#8122)

Explain which folders to persist outside apache/hop-web, how to
configure HOP_CONFIG_FOLDER, and how auth and project access survive
image upgrades.

Author: mattcasters

docs/hop-dev-manual/modules/ROOT/pages/hopweb/developer-guide.adoc

@@ -114,6 +114,11 @@ The main configuration of Hop is done through a single configuration file called
 It is possible to set pass this standard Hop environment variable `HOP_CONFIG_FOLDER` to the docker container.
 You can point it to a mounted volume for example:
 
-`docker run -p 8080:8080 -v /host/path/to/config:/config -e HOP_CONFIG_FOLDER=/config hop-web`
+`docker run -p 8080:8080 -v /host/path/to/config:/hop/config -e HOP_CONFIG_FOLDER=/hop/config hop-web`
+
+Prefer a dedicated path such as `/hop/config` rather than `/config`.
+The Hop Web image uses `/config` for an optional Tomcat `tomcat-users.xml` / `web.xml` overlay.
 
 In the same way you can set the standard variable `HOP_AUDIT_FOLDER` to store GUI auditing and logging information.
+
+For the operator-facing volume layout, Compose example, and upgrade procedure, see xref:tech-manual::hop-web-docker.adoc[Hop Web in Docker: persistence and upgrades].

docs/hop-tech-manual/modules/ROOT/nav.adoc

@@ -16,6 +16,7 @@ under the License.
 ////
 * xref:getting-started.adoc[Getting started]
 * xref:docker-container.adoc[Docker container]
+* xref:hop-web-docker.adoc[Hop Web in Docker]
 * xref:disable-ui-elements.adoc[Disable UI elements]
 * xref:hop-vs-kettle/index.adoc[Kettle/PDI and Hop]
 ** xref:hop-vs-kettle/hop-vs-kettle.adoc[Hop vs Kettle]

docs/hop-tech-manual/modules/ROOT/pages/docker-container.adoc

@@ -31,6 +31,9 @@ It's a **Hop Docker image** supporting both **short-lived** and **long-lived** s
 A short-lived setup executes a pipeline or workflow and stops right after.
 A long-lived setup starts a Hop server and waits for work.
 
+This page describes `apache/hop` (hop-run and Hop Server).
+For the Hop Web GUI image (`apache/hop-web`), including which folders to persist across upgrades, see xref:hop-web-docker.adoc[Hop Web in Docker: persistence and upgrades].
+
 == Operating system
 
 The docker container runs a minimal Linux system called https://hub.docker.com/_/alpine[Alpine].
@@ -48,6 +51,7 @@ The Linux user used to execute in the container is `hop` and the group is `hop`
 |```/files```
 | This volume has read-write permissions for Linux user `hop`.
 You can use it for example to mount a folder that contains the **hop and project config** as well as the **workflows and pipelines**.
+Do not persist project files only under `/opt/hop`; that tree is replaced when you pull a new image.
 
 |```/home/hop```
 | The initial working directory location of the docker container.
@@ -70,6 +74,18 @@ Use one of: `None`, `Error`, `Minimal`, `Basic`, `Detailed`, `Debug` or `Rowleve
 |`/opt/hop/hop.err.log`
 | The file path to the Hop log file.
 
+|```HOP_CONFIG_FOLDER```
+|
+| Folder that contains `hop-config.json` (project and environment registrations, GUI settings).
+Leave unset to use the image default (`config/` under the Hop install).
+Point this at a mounted volume if the configuration must survive replacing the container.
+See xref:hop-web-docker.adoc[Hop Web in Docker] for the Hop Web layout; the same variable applies here.
+
+|```HOP_AUDIT_FOLDER```
+|
+| Folder for GUI / execution audit data.
+Point this at a mounted volume to keep it across container recreation.
+
 |```HOP_PROJECT_NAME```
 |
 | Name of the Hop project to create in the container.
@@ -392,6 +408,7 @@ In this example, a project is created in the container and exposed in the Hop Py
 
 NOTE: The option to run commands is available from Hop version 2.18.
 
+[[DownloadingJDBCDrivers]]
 == Downloading JDBC drivers
 
 Apache Hop ships the JDBC drivers it is allowed to redistribute (PostgreSQL, MS SQL Server, Snowflake, ...). Drivers with a restricted license - Oracle, MySQL, MariaDB, IBM DB2 and others - are *not* bundled and have to be added to the `lib/jdbc` folder yourself.