Group accounts by user in generated html

[razum2um]

Currently all credentials, certificates and configs are grouped under specific service e.g. all accounts on openconnect page, same list on openvpn and wireguard.

This is already makes some troubles for someone: #81 (comment)
Besides, this makes extra communication/memory required about which accounts are already taken, which not.

I suggest to make an optional choice before html generation and (besides the old format) generate N times same html under account name directories, and each nginx location will be served to the only one account

p.s. there's only 1 ssh private key and a single http-auth entry, but why no to make an ssh key and htpasswd per account as well?

p.p.s. actually, if some common, system-wide steps will be idempotent, running streisand one more time in this mode will just create another N accounts, as requested here: #81