Resource: add static validation for all the known resource types

[eolivelli]

Summary:

• validate as much as possible all the known resource types: datasource (astra, cassandra, pinecone, generic JDBC), vector-database (astra, pinecone, cassandra), openai-configuration, vertex-configuration, hugging-face-configuration
• the intent is to fail invalid configurations at deploy time

Notes:

• we are validating resources that are actually used by agents, this allows to have some demo configuration files with empty values: they won't fail the deploy as long as they are not used
• we cannot connect to the services at deploy time, this is because the actual connection can be performed ONLY from the agent pods, and not from the Control Plane, due to security reasons (agent runners run in special security contexts) and also because the .nar files with the drivers are only available up there