WIP: docs: document which services are involved in delivering an internal msg

[missytake]

Pulled out of #673

[Simon-Laux]

github shows an error when attempting to render the diagram, looks like spaces inside of names are not supported.

Suggested change

	graph LR;
	chatmail core --> |465|smtps/smtpd;
	chatmail core --> |587|submission/smtpd;
	smtps/smtpd --> |10080|filtermail;
	submission/smtpd --> |10080|filtermail;
	filtermail --> |10025|smtpd reinject;
	smtpd reinject --> cleanup;
	cleanup --> qmgr;
	qmgr --> smtpd accepts message;
	qmgr --> |lmtp|dovecot;
	dovecot --> chatmail core;
	graph LR;
	chatmail_core --> |465|smtps/smtpd;
	chatmail_core --> |587|submission/smtpd;
	smtps/smtpd --> |10080|filtermail;
	submission/smtpd --> |10080|filtermail;
	filtermail --> |10025|smtpd_reinject;
	smtpd_reinject --> cleanup;
	cleanup --> qmgr;
	qmgr --> smtpd_accepts_message;
	qmgr --> |lmtp|dovecot;
	dovecot --> chatmail_core;

or if you want to keep the names without _:

Suggested change

	graph LR;
	chatmail core --> |465|smtps/smtpd;
	chatmail core --> |587|submission/smtpd;
	smtps/smtpd --> |10080|filtermail;
	submission/smtpd --> |10080|filtermail;
	filtermail --> |10025|smtpd reinject;
	smtpd reinject --> cleanup;
	cleanup --> qmgr;
	qmgr --> smtpd accepts message;
	qmgr --> |lmtp|dovecot;
	dovecot --> chatmail core;
	graph LR;
	chatmail_core["chatmail core"] --> |465|smtps/smtpd;
	chatmail_core --> |587|submission/smtpd;
	smtps/smtpd --> |10080|filtermail;
	submission/smtpd --> |10080|filtermail;
	filtermail --> |10025|smtpd_reinject;
	smtpd_reinject["smtpd reinject"] --> cleanup;
	cleanup --> qmgr;
	qmgr --> smtpd_accepts_message["smtpd accepts message"];
	qmgr --> |lmtp|dovecot;
	dovecot --> chatmail_core;

there are sites like https://mermaid.live where you can edit mermaid diagrams with live preview.