feat: implement PdfService using mikehaertl/php-pdftk

[luka-nextcloud]

• Resolves:
• Target version: main

Summary

Follow-up

• Setup check to suggest installing pdftk
• Template creator for PDF files Template creator for PDF files #3867
• Tests

[juliushaertl]

Some comments inline :)

[juliushaertl]

@luka-nextcloud I pushed a few fixes while reviewing testing. Mainly to make the matching of fields work when fillling in to what is described below and to not overwrite the existing file

@elzody I extended the OCS API also to be able to pass a destination along. However I noticed we have not really typed the fields array structure in the server API and here. Currently it seems to just use array<int,array{content: string}>. We should properly document that in the server API and all methods around here. What I currently lack to know is if the array key is actually using the Field class index value or is just a numeric index based on what the vue frontend in files loops over.

Sample curl commands

 curl -H 'OCS-APIRequest: true' https://admin:admin@nextcloud.local/ocs/v2.php/apps/richdocuments/api/v1/template/fields/extract/37526\?format\=json
 
 curl -X POST -H 'OCS-APIRequest: true' https://admin:admin@nextcloud.local/ocs/v2.php/apps/richdocuments/api/v1/template/fields/fill/37526\?format\=json -H "Content-Type: application/json" --data '{"fields":[{"content":"FooBar"}],"destination":"foobar.pdf"}'

[elzody]

@juliushaertl The index should be the string index from the field class, afaik. The second curl command looks like it should have something like '{"fields":["someIndex": {"content":"FooBar"}],"destination":"foobar.pdf"}', else I'm not sure how it would know which form control the content being passed belongs to

[juliushaertl]

All right, the extra object with a content property originates from the Collabora API?

[elzody]

@juliushaertl I think so, if I remember correctly you pass the fields to the endpoint in richdocuments as an array, and it loops over the fields passed and extracts the form control index and its matching properties (content, alias, etc.) then passes an object looking something like this to the Collabora API in JSON format:

{
  "ContentControls.ByIndex.0": {
    "content": "Something"
  },
  "ContentControls.ByIndex.1": {
    "alias": "Something else"
  }
}

And yeah because it allows changing multiple controls at a time the index is needed to specify what data each control should have via its index. Hopefully that makes sense, not sure if that's what you're asking

[juliushaertl]

/backport to stable30