docs(chore): Normalize for consistency (#2206)

"Brief" summary/overview of changes. See the PR discussion or individual commits from the PR for more details.

---

Only applies to the `docs/content/**` content (_and `setup` command_). `target/` and `test/` can be normalized at a later date.

* Normalize to `example.com`

- Domains normalized to `example.com`: `mywebserver.com`, `myserver.tld`, `domain.com`, `domain.tld`, `mydomain.net`, `my-domain.tld`, `my-domain.com`, `example.org`, `whoami.com`.
- Alternative domains normalized to `not-example.com`: `otherdomain.com`, `otherdomain.tld`, `domain2.tld`, `mybackupmx.com`, `whoareyou.org`.
- Email addresses normalized to `admin@example.com` (in `ssl.md`): `foo@bar.com`, `yourcurrentemail@gmail.com`, `email@email.com`, `admin@domain.tld`.
- Email addresses normalized to `external-account@gmail.com`: `bill@gates321boom.com`, `external@gmail.com`, `myemail@gmail.com`, `real-email-address@external-domain.com`.
- **`faq.md`:** A FAQ entry title with `sample.domain.com` changed to `subdomain.example.com`.
- **`mail-fetchmail.md`:** Config examples with FQDNs for `imap`/`pop3` used `example.com` domain for a third-party, changed to `gmail.com` as more familiar third-party/external MTA.

* Normalize config volume path

- Normalizing local config path references to `./docker-data/dms/config/`: `./config/`, `config/`, \``config`\`, `/etc/` (_volume mount src path prefix_).
- Normalize DMS volume paths to `docker-data/dms/mail-{data,state,log}`: `./mail`, `./mail-state` `./data/mail`, `./data/state`, `./data/logs`, `./data/maildata`, `./data/mailstate`, `./data/maillogs`, (_dropped/converted data volumes: `maildata`, `mailstate`_).
- Other docker images also adopt the `docker-data/{service name}/` prefix.

* `ssl.md` - Use `dms/custom-certs` where appropriate.

* Apply normalizations to README and example `docker-compose.yml`

---

Common terms, sometimes interchangeably used or now invalid depending on context: `mail`, `mail container`, `mail server`, `mail-server`, `mailserver`,`docker-mailserver`, `Docker Mailserver`.

Rough transformations applied to most matches (_conditionally, depending on context_):

- 'Docker Mailserver' => '`docker-mailserver`'
- 'mail container' => '`docker-mailserver`' (_optionally retaining ' container'_)
- 'mail server' => 'mail-server' / '`docker-mailserver`'
- 'mail-server' => '`docker-mailserver`'
- 'mailserver' => 'mail-server' / '`docker-mailserver`'

Additionally I checked `docker run` (_plus `exec`, `logs`, etc, sub-commands_) and `docker-compose` commands. Often finding usage of `mail` instead of the expected `mailserver`

Additionally changes `mailserver` hostname in k8s to `mail` to align with other non-k8s examples.

---

* drive-by revisions

Mostly minor revisions or improvements to docs that aren't related to normalization effort.

docs/content/config/advanced/mail-fetchmail.md

@@ -10,10 +10,10 @@ environment:
   - FETCHMAIL_POLL=300
 ```
 
-Generate a file called `fetchmail.cf` and place it in the `config` folder. Your `docker-mailserver` folder should look like this example:
+Generate a file called `fetchmail.cf` and place it in the `docker-data/dms/config/` folder. Your `docker-mailserver` folder should look like this example:
 
 ```txt
-├── config
+├── docker-data/dms/config
 │   ├── dovecot.cf
 │   ├── fetchmail.cf
 │   ├── postfix-accounts.cf
@@ -28,13 +28,13 @@ A detailed description of the configuration options can be found in the [online
 
 ### IMAP Configuration
 
-!!! example 
+!!! example
 
     ```fetchmailrc
-    poll 'imap.example.com' proto imap
+    poll 'imap.gmail.com' proto imap
       user 'username'
       pass 'secret'
-      is 'user1@domain.tld'
+      is 'user1@example.com'
       ssl
     ```
 
@@ -43,15 +43,16 @@ A detailed description of the configuration options can be found in the [online
 !!! example
 
     ```fetchmailrc
-    poll 'pop3.example.com' proto pop3
+    poll 'pop3.gmail.com' proto pop3
       user 'username'
       pass 'secret'
-      is 'user2@domain.tld'
+      is 'user2@example.com'
       ssl
     ```
 
 !!! caution
-    Don’t forget the last line: eg: `is 'user1@domain.tld'`. After `is` you have to specify one email address from the configuration file `config/postfix-accounts.cf`.
+
+    Don’t forget the last line! (_eg: `is 'user1@example.com'`_). After `is`, you have to specify an email address from the configuration file: `docker-data/dms/config/postfix-accounts.cf`.
 
 More details how to configure fetchmail can be found in the [fetchmail man page in the chapter “The run control file”][fetchmail-docs-run].