Is your feature request related to a problem?

Extensions may depend on other extensions. For example, a machine learning model may depend on data cleaning and preparation by another extension, or other analogs to an ETL pipeline. By design, extensions will not be required or expected to communicate directly with each other, which means the Extensions Orchestrator must provide a means to:

1. Allow extensions to discover whether their dependent extensions are installed and available
2. Orchestrate workflows involving multiple extensions, where completion of a step by one extension triggers an action by another extension.

What solution would you like?

• Extensions need a mechanism to define dependencies: [FEATURE] Update DiscoveryExtension to include dependency information #151
• Extensions need to be able to query the Orchestrator to validate their dependencies are initialized: [FEATURE] Let an extension query OpenSearch for all initialized extensions #149
• The Extension Orchestrator must provide the ability to relay request/response actions across extensions: [FEATURE] Relay Request/Response actions between extensions #152

What alternatives have you considered?

• Not allowing dependent extensions and requiring complex dependencies as described to be declared in a larger, monolithic extension. This reduces the modularity and re-use of components and increases complexity and error potential.
• Allowing extensions to directly communicate with each other to accomplish these goals. While we have no means to specifically prohibit this, we also have no way to require it and enable it to be accomplished securely so we should not rely on its availability.

Do you have any additional context?

This relates to #65 which in turn related to comments on #60.

It is conceivable that a workflow capability (and perhaps some of the discovery work) could be part of some core features of the Job Scheduler.