[bug] Strategy cache hash should not depend solely on the file itself

[choinek]

Changing the strategy in request obviously doesn't change anything when the cache is used (even if OCR was performed using a different strategy).

• Analyze which fields could critically interfere with the results (I guess it's file_hash + strategy_name + language).
• Combine them (it's not necessary to hash them after proper validation; it could be language:strategy_name:file_hash).

[pkarw]

This is certainly a good one ☝️