# ----------------------------------------------------------------------
# | Cache Control                                                      |
# ----------------------------------------------------------------------

# Serve resources with appropriate cache control directives.
#
# The `Cache-Control` header field holds directives (instructions) that control
# caching in browsers and shared caches (e.g. Proxies, CDNs).
# Its use targets web performances improvement by specifying the expected
# client and network caches behaviors.
#
# The usable cache directives are listed here:
# https://www.iana.org/assignments/http-cache-directives/http-cache-directives.xml
#
# The cache directives are documented here:
# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control#response_directives
#
# (!) Enable and configure this configuration with care.
#     Default values should embrace conformance for static files and simple
#     apps, but cache control definition at backend level is highly preferred.
#     Incorrect directives can lead to data leaks, or can degrade performances.
#
#     More specifically, in-depth understanding on `public` vs `private`
#     directives meanings is highly recommended. A resource with `public` will
#     be cached by shared caches like CDN, even if a user session is active.
#
# (*) To avoid duplication of the directive `no-cache` on `Cache-Control`,
#     the value is skipped here.
#     The directive `no-cache` is already defined by Nginx `expires` when set
#     to `epoch`. This ensure a correct value enforcement whenever cache
#     control configuration is used or not.
#     Cache expiration configuration `expires` is described in the file
#     h5bp/web_performance/cache_expiration.conf.
#     https://nginx.org/en/docs/http/ngx_http_headers_module.html#expires
#
# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
# https://www.rfc-editor.org/rfc/rfc9111.html
# https://www.rfc-editor.org/rfc/rfc8246.html
# https://www.rfc-editor.org/rfc/rfc5861.html
# https://www.iana.org/assignments/http-cache-directives/http-cache-directives.xml
# https://cache-tests.fyi/

add_header Cache-Control $cache_control;