chore: use github var for kurrentdb images

[w1am]

No description provided.

[Copilot]

Pull Request Overview

This PR updates how Docker images are referenced for KurrentDB by consolidating multiple image parts (registry, image name, version) into a single environment variable. Key changes include:

• Removing the registry and version constants and builder methods in favor of a unified DEFAULT_IMAGE.
• Updating all CI/CD workflows and Docker Compose configurations to use the KURRENTDB_IMAGE variable.
• Adjusting documentation and workflow job names to reflect the new image variable usage.

Reviewed Changes

Copilot reviewed 14 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/test/java/io/kurrent/dbclient/databases/DockerContainerDatabase.java	Removed registry/version fields and adjusted constructor to use a single image reference.
src/test/java/io/kurrent/dbclient/DatabaseFactory.java	Updated builder configuration to use KURRENTDB_IMAGE from the environment.
docker-compose.yml	Revised image specification to rely on KURRENTDB_IMAGE.
README.md	Updated badges and documentation links reflecting CI changes.
.github/workflows/*.yml	Consolidated image environment variables to KURRENTDB_IMAGE and modified some job naming conventions.
.github/ISSUE_TEMPLATE/*	Added/updated issue template configurations.

Files not reviewed (2)

• .github/workflows/docker-repo.yml: Language not supported
• .github/workflows/test-dispatch.yml: Language not supported

Comments suppressed due to low confidence (2)

src/test/java/io/kurrent/dbclient/databases/DockerContainerDatabase.java:56

• [nitpick] Since the registry and version details are removed, consider adding a comment that the builder.image value must include the full image name (registry, image, tag) as expected by downstream consumers.

super(builder.image);

.github/workflows/build.yml:30

• The removal of the 'tests' and 'plugins-tests' jobs from build.yml might reduce overall test coverage in the CI pipeline. Please ensure that tests previously executed in this workflow are now adequately covered in the updated pipeline configuration.

# Tests that do not require a database connection.