EZP-30554: Purge several keys at once to simplify debug & reduce round trips

[andrerom]

Question	Answer
JIRA issue	EZP-30554
Type	Improvement
Target version	0.9
BC breaks	no
Doc needed	maybe

As of 2.5LTS we require Varnish 5.1 or higher, meaning we can take advantage of varnish-modules 0.10+ support for several keys in header while purging. In order to:

• Simplify Varnish debugging when checking purge requests
• Reduce rountrips on between web server and varnish for purges

Given the package is also allowed to be used on 1.13, which supports Varnish 4.x. Should we ❓

• A. Expose a setting for this as currently is the case in this PR
• B. Avoid complexity of a temprary setting, and rather tell 1.13 + Varnish 4.x users to use ezplatform-http-cache 0.8.x.

TODO:

• Implement feature / fix a bug.
• Implement tests + specs and passing ($ composer test)
• Fix new code according to Coding Standards ($ composer fix-cs).
• Ask for Code Review.

[adamwojs]

Given the package is also allowed to be used on 1.13, which supports Varnish 4.x. Should we ❓

My answer is:

B. Avoid complexity of a temprary setting, and rather tell 1.13 + Varnish 4.x users to use ezplatform-http-cache 0.8.x.

[andrerom]

@adamwojs & @vidarl updated

[kmadejski]

Just a two tiny nitpicks, besides that 👍