Add Twig filter for resolve path to cache

[peter-gribanov]

Q	A
Branch?	2.0
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#1346
License	MIT
Doc PR

Add a imagine_filter_cache new Twig filter what always return URL to cached image, even if there is no cache. Proper use of this filter can improve performance.

If you always warm up the cache, then you do not need to check the existence of the cached image every time when rendering templates. You can immediately use the link to the cached version of the image.

Also, you can avoid unnecessary controller calls if you use the local filesystem to store the image cache and use the same cache path as in the controller.

# /etc/nginx/nginx.conf
map $http_accept $webp_suffix {
    "~*webp"  ".webp";
}

server {
    # ...

    location ~ ^/media/cache {
        expires 365d;
        access_log off;
        add_header Cache-Control "public";
        try_files $uri$webp_suffix $uri /index.php$is_args$args;
    }

    # ...
}

# config/packages/liip_imagine.yaml
liip_imagine:
    resolvers:
       profile_photos:
          web_path:
            web_root: "%kernel.root_dir%/../public"
            cache_prefix: "media/cache"
    webp:
        generate: true

# config/routes/liip_imagine.yaml
liip_imagine_filter:
    path: /media/cache/{filter}/{path}
    defaults:
        _controller: '%liip_imagine.controller.filter_action%'
    methods:
        - GET
    requirements:
        filter: '[A-z0-9_-]*'
        path: .+

[coveralls]

Coverage increased (+0.04%) to 84.104% when pulling 0e71655 on peter-gribanov:twig_filter into 7a1779b on liip:2.x.

[dbu]

thanks a lot!

do you want to add the nginx trick to use this even without async cache warming to the documentation? (it would also prevent race conditions when a new image is uploaded and immediately looked at)