Use latest stable Haystack in Hayhooks Docker image

[anakin87]

Problem

Hayhooks Docker image is currently based on deepset/haystack:base-main.
This means that if we release the new Docker image (e.g. deepset/hayhooks:v1.8.0), the image will include whatever version of Haystack happens to be on main at build time.

As a user, I would expect it to install the latest stable release of Haystack.

(For deepset/hayhooks:main, I find it correct to point at Haystack main)

Potential solutions

Since deepset/haystack does not provide latest or stable tags, we cannot automatically rely on the upstream image.

• add latest or stable tags to Haystack image: this means applying the change on Haystack and waiting for the next Haystack release before updating Hayhooks
• do not build upon deepset/haystack but start for example from python:3.12-slim (base ofdeepset/haystack image) and install the latest stable version of Haystack based on projects requirements.