Bump version to 1.15.0

[jBonoraW]

:tophat: What?

Bump version to 1.15.0 Update the documentation Update the changelog

:thinking: Why?

release new features:

1.15.0 (2024-02-29)

• [Added] Add a setting CLIENT_OPTIONS for Pub/Sub clients (#274)
• [Changed] Use api_endpoint from CLIENT_OPTIONS to check loss of network connectivity(#275)

:link: Related issue

Solves #277