www/caddy: Changes needed for Caddy v.2.8.0

[Monviech]

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The new Caddy version will have some small breaking changes that influence the template generation of the os-caddy plugin.

https://github.com/caddyserver/caddy/releases/tag/v2.8.0-beta.1

Changes that need to be made:

• [x] Make ACME E-Mail a required field, so Zerossl and Lets Encrypt continue to work at the same time. https://github.com/opnsense/plugins/pull/3960
• [x] Rename the basicauth directive to basic_auth in the Caddyfile template. Since my implementation uses bcrypt by default, the deprecation of scrypt can be ignored. https://github.com/opnsense/plugins/pull/3961

[Monviech]

Handled by other tickets.