EZP-30857: Fixed assessment of image removal feasibility

[alongosz]

Question	Answer
JIRA issue	EZP-30857
Alternative to	#2835
Required by	#3057
Bug/Improvement	yes
Target version	7.5, ezplatform-kernel:1.1+
BC breaks	no
Doc needed	no

When removing a Content item (or its Version) with a changed Image Field Type file, the file associated with a previous Version was not deleted from a file system.

This happened because relation of ezimagefile.contentobject_attribute_id to ezcontentobject_attribute.id does not contain Version number (attribute - a.k.a. Field - ID is the same for every Version).
One of the approaches would be to introduce versioning for ezimagefile (#2835). This however always causes issues due to BC break on schema.

Instead, I'm proposing an alternative - change of assessment if image can be removed based on ezimage data_text XML, which contains proper URI for a given Version. Instead of getting a count against a product of ezimagefile and ezcontentobject_attribute, data is fetched and processed to find the actual file system file URI for a given Version.

The count cannot work because the resulting Cartesian product (slice/intersection of data) is incorrect - joins file paths for all Versions with a Field. The join itself is kept to make sure we're joining existing ezimage entry (7dca764).

Additionally, I've discovered that image variations (aliases) are not removed at all. It didn't work because a produced file path was in the form of ../var/site/storage/images/_aliases/medium/var/site/storage/images/....
Fixed it by applying removal service on a relative original binay file identifier (41a0e43).

I've discovered two other CS and DX issues, but for now I'll make follow-up PRs. Moreover we deal here with a responsibility mixup - Doctrine Gateway should not process XML but just return data. That however is a candidate for ezplatform-kernel:master - see ezsystems/ezplatform-kernel#96.

QA

• Filesystem state before/after Content & Version removal as described in the JIRA ticket.
• Regression against EZP-30857.
• Image variations (aliases) removal (can be generated by e.g. embedding image into a content - image and content removal did not delete variations).

Note: Physical files can be found (and should not be found after deleting) by the following command:

find web/var/site/storage -type f

TODO:

• Wait for Travis.
• Fix a bug.
• Implement tests.
• Fix new code according to Coding Standards ($ composer fix-cs).
• Fix removal of aliases (image variations)
• Shift responsibility of processing XML from Doctrine Gateway to Storage handler (EZP-31793: Moved Image FieldType XML processing to ImageStorage ezplatform-kernel#96)
• Ask for Code Review.

[mnocon]

Tested together with #3057

[cmateo]

So, now the images are deleted from disk. But that will apply on future action of removing content. What about images that were not previously deleted ?