Fixes #670 - Added Elasticsearch 9 support

Author: ralf401

install/elasticsearch.rst

@@ -12,19 +12,19 @@ recommended**).
 Step 1: Installation
 --------------------
 
-Elasticsearch offers different versions. Currently, the versions 7 and 8
+Elasticsearch offers different versions. Currently, the versions 7, 8 and 9
 are supported by Zammad. For installation instructions, you should first and
 foremost follow
-`Elastic's installation documentation <https://www.elastic.co/guide/en/elasticsearch/reference/8.x/setup.html>`_.
-Use the dropdown in the top left corner to choose which version you want to
+`Elastic's installation documentation <https://www.elastic.co/docs/deploy-manage/deploy/self-managed/installing-elasticsearch>`_.
+Use the dropdown in the top right corner to choose which version you want to
 install.
 
 However, if you want go with Elasticsearch 7 (which is slightly easier to
 install), you can find the consolidated installation steps below.
 Be aware that the maintenance of version 7 might be stopped earlier than for
 later versions, which also come with some additional security features.
 
-.. hint:: If you are installing Elasticsearch 8 and want to follow our
+.. hint:: If you are installing Elasticsearch 8 or newer and want to follow our
    standard configuration in step 2, make sure to copy/save the password which
    is shown while installing Elasticsearch.
 
@@ -240,16 +240,15 @@ Elasticsearch URL
 
       $ sudo zammad run rails r "Setting.set('es_url', 'http://localhost:9200')"
 
-   Elasticsearch 8:
+   Elasticsearch 8+:
 
    .. code-block:: sh
 
       $ sudo zammad run rails r "Setting.set('es_url', 'https://localhost:9200')"
 
 
 Elasticsearch user and password (only for Elasticsearch >= 8)
-   Now you need your password which was shown to you while installing
-   Elasticsearch.
+   Now you need your password which was shown during the installation.
 
    Set Elasticsearch user:
 

prerequisites/software.rst

@@ -171,11 +171,11 @@ Please follow the official guides and ensure to set it up in a secure way.
 2.6 Elasticsearch (optional)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Zammad uses Elasticsearch to
+Zammad uses Elasticsearch to:
 
-   1) make the search faster
-   2) support advanced features like reports
-   3) search for content of email attachments
+   1) make the search faster,
+   2) support advanced features like reports,
+   3) search for content of email attachments.
 
 This becomes increasingly important the higher the number of tickets in your
 system gets.
@@ -187,18 +187,12 @@ system gets.
    the search will be very limited. We recommend using Elasticsearch, as it will
    boost the usage of Zammad greatly!
 
-.. hint:: 📦 **If you install Zammad via package manager...**
-
-   It's perfectly safe to manually override the Elasticsearch dependency.
-   The appropriate command line flag will depend on your platform
-   (e.g. ``--force``, ``--ignore-depends``, ``--skip-broken``);
-   check your package manager's manpage to find out.
-
 .. csv-table:: Zammad/Elasticsearch version compatibility
    :header: "Zammad", "Elasticsearch"
    :widths: 20, 20
 
-   "5.2+", ">= 7.8, < 9"
+   "7.0+", ">= 7.8, < 10"
+   "5.2 - 6.5", ">= 7.8, < 9"
    "5.0 - 5.1", ">= 7.8, < 8"
    "4.0-4.1", ">= 6.5, <= 7.12"
    "3.4-3.6", ">= 5.5, <= 7.9"
@@ -211,6 +205,13 @@ An Elasticsearch plugin is required for version 7 or older to index the
 contents of email attachments: ``ingest-attachment``. Starting with
 Elasticsearch 8, it is included by default.
 
+.. hint:: You can override the Elasticsearch dependency for package
+   installations (not recommended!)
+
+   It depends on your system how to manually override the Elasticsearch
+   dependency (e.g. ``--force``, ``--ignore-depends``, ``--skip-broken``);
+   check your package manager's manpage to find out.
+
 2.7 Memcached
 ^^^^^^^^^^^^^