retention: Add some more system documentation.
retention: Add some more system documentation.

timabbott/zulip,kou/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,brainwane/zulip,andersk/zulip,rht/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,showell/zulip,brainwane/zulip,synicalsyntax/zulip,showell/zulip,punchagan/zulip,punchagan/zulip,synicalsyntax/zulip,rht/zulip,brainwane/zulip,andersk/zulip,synicalsyntax/zulip,hackerkid/zulip,timabbott/zulip,brainwane/zulip,rht/zulip,kou/zulip,zulip/zulip,rht/zulip,brainwane/zulip,showell/zulip,zulip/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,timabbott/zulip,andersk/zulip,timabbott/zulip,rht/zulip,timabbott/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,hackerkid/zulip,showell/zulip,zulip/zulip,rht/zulip,hackerkid/zulip,eeshangarg/zulip,punchagan/zulip,eeshangarg/zulip,brainwane/zulip,punchagan/zulip,punchagan/zulip,synicalsyntax/zulip,hackerkid/zulip,hackerkid/zulip,timabbott/zulip,brainwane/zulip,synicalsyntax/zulip,kou/zulip,synicalsyntax/zulip,synicalsyntax/zulip,hackerkid/zulip,showell/zulip,andersk/zulip,zulip/zulip,showell/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,timabbott/zulip,showell/zulip