Edit Documents with Rhai

[Kerollmops]

This PR introduces a first version of the Update Documents with Function (internal). It uses the Rhai programming language to let users express the modifications they want apply.

You can read more about the way to use this functions on the Usage PRD Page. The prototype is available through Docker by using the following command:

docker run -p 7700:7700 -v $(pwd)/meili_data:/meili_data getmeili/meilisearch:prototype-edit-documents-with-rhai-3

TODO

• Support the DocumentEdition task in dumps.
• Remove the unwraps and panics.
• Improve error codes for the function parameter.
• Check that the script cannot do any io.
• Introduce a Documents.edit action or require the Documents.all action.
• Change the editionCode to the clearer function field name in the tasks.
• Support a user provided context and maybe more (but keep function execution isolated for reproducibility).
• Support deleting documents when the doc is () (nil, null).
• Support canceling document edition.
• Multithread document edition by using rayon (and rayon-par-bridge).
• Limit the number of instruction by function execution.
• Expose the limit of instructions in the settings. Not sure, in fact.
• Ignore unmodified documents in the tasks count.
• Make the filter field optional (not forced to be null).