External Analyser / Feature: Boilerplate Implementation

[ppanopticon]

Task Description

Certain features rely on external services (e.g., a neural network in Python). vitrivr-engine should offer facilities, to access such features using a web-service architecture.

• [x] Interface Definition: For communication, the external service and vitrivr-engine should communicate using a well-defined RESTful interface via HTTP / HTTPS. Generally, vitrivr-engine sends some type of Content to the service and retrieves some sort of Descriptor(s).
• [x] Abstract Implementation: To speed-up development, vitrivr-engine should sport abstract ExternalAnalyser, ExternalRetriever and ExternalExtractor implementations, that can be parameterised to invoke a specific, external service adhering to aforementioned interface definitions. Potential parameters could be host, port, feature etc.
• [x] Reference Implementations: The mechanism should be implemented as two concrete features for CLIP and DINOv2.

The external service(s) can and should be hosted in a dedicated repository. Optionally, one could make this service configurable and extensible in terms of what concrete features it hosts (i.e., build a feature server).

Dependencies

• Extractor, Retriever and Analyser implementations
• Schema and SchemaManager

Boundary conditions

• Communication should be standardised using Open API (if possible)
• Named parameters can be provided with the schema definition (see Schema and SchemaManager)

[rahelarnold98]

I've successfully implemented the requested feature for external service integration. The changes are on the external-descriptors branch. Here's a summary of what's been done:

• Added abstract implementations for ExternalAnalyser, ExternalRetriever, and ExternalExtractor.
• Implemented concrete features for CLIP and DINOv2 as reference implementations.
• Created a dedicated repository for external services: vitrivr/vitrivr-python-descriptor-server.

I've created the corresponding pull request #15, as the issue is now completed. Once it is reviewed, I will merge the pull request.

[ppanopticon]

I merged your PR. Generally, I did some cleanup and adjusted everything to work with the recent changes.

I also left a few TODOs. Could you please have a look at them?