Update default Kafka image to avoid pull restrictions and ensure module reliability

[igor-soldev]

Hi,

I noticed that kafka/main.go defines the default image repository as:
const defaultImageRepository = "bitnami/kafka"

The Problem
Bitnami has restricted public access to their Docker images (legacy tags are frozen, newer ones often require auth).
Since Dagger modules are designed to be reusable building blocks for CI/CD pipelines, relying on bitnami/kafka as the default often leads to pull access denied errors, breaking pipelines for users trying to use this module out-of-the-box.

Proposed Solution
I suggest changing the default to soldevelo/kafka.
This image is a free, drop-in replacement that preserves the Bitnami directory layout and environment variable structure. This ensures that any internal logic in your module (that might expect specific paths like /opt/bitnami/...) continues to work without modification.

Suggested Change in kafka/main.go:

// Old
const defaultImageRepository = "bitnami/kafka"

// New
const defaultImageRepository = "soldevelo/kafka"

I can submit a Pull Request to apply this one-line change. Would you be open to that?