docs(refactor): Restructure document hierarchy

Additionally rename `installation-examples.md` and split

docs/content/config/advanced/full-text-search.md

@@ -0,0 +1,58 @@
+---
+title: 'Full-Text Search'
+---
+
+## Overview
+
+Full-text search allows all messages to be indexed, so that mail clients can quickly and efficiently search messages by their full text content.
+
+The [dovecot-solr Plugin](https://wiki2.dovecot.org/Plugins/FTS/Solr) is used in conjunction with [Apache Solr](https://lucene.apache.org/solr/) running in a separate container. This is quite straightforward to setup using the following instructions.
+
+## Setup Steps
+
+1. `docker-compose.yml`:
+
+    ```yaml
+      solr:
+        image: lmmdock/dovecot-solr:latest
+        volumes:
+          - solr-dovecot:/opt/solr/server/solr/dovecot
+        restart: always
+
+      mailserver:
+        image: tvial/docker-mailserver:latest
+        ...
+        volumes:
+          ...
+          - ./etc/dovecot/conf.d/10-plugin.conf:/etc/dovecot/conf.d/10-plugin.conf:ro
+        ...
+
+    volumes:
+      solr-dovecot:
+        driver: local
+    ```
+
+2. `etc/dovecot/conf.d/10-plugin.conf`:
+
+    ```conf
+    mail_plugins = $mail_plugins fts fts_solr
+
+    plugin {
+      fts = solr
+      fts_autoindex = yes
+      fts_solr = url=http://solr:8983/solr/dovecot/ 
+    }
+    ```
+
+3. Start the solr container: `docker-compose up -d --remove-orphans solr`
+
+4. Restart the mailserver container: `docker-compose restart mailserver`
+
+5. Flag all user mailbox FTS indexes as invalid, so they are rescanned on demand when they are next searched: `docker-compose exec mailserver doveadm fts rescan -A`
+
+
+## Further Discussion
+
+See [#905][github-issue-905]
+
+[github-issue-905]: https://github.com/docker-mailserver/docker-mailserver/issues/905