Awkward "skip API call" implementation

[bbenligiray]

While declaring an endpoint, one can omit operation, which means the API call is to be skipped, and the fulfillment will depend on pre/post processing https://docs.api3.org/reference/ois/latest/processing.html#skip-the-api-call This works fine, but there are some issues with the implementation

airnode/packages/airnode-node/src/api/index.ts

Line 291 in 031919e

if (!endpoint.operation && isEmpty(endpoint.fixedOperationParameters)) {

• The implementation require operation to not be defined and fixedOperationParameters to be empty to skip the call. Instead, the implementation should only require operation to not be defined, and the fact that fixedOperationParameters is empty should be validated.
• The implementation throws if operation is not defined and both pre-processing and post-processing are empty. These should be validated instead of checking at runtime.
• When an endpoint doesn't define an operation, none of its parameters should have an operationParameter defined. It's currently not possible to not define an operationParameter for an endpoint parameter, so the only way to use this feature is to map these endpoints to dummy operation parameters. This issue is not specific to skipping API calls and is tracked in Allow endpoint parameters to not be mapped to operation parameters #1800

[bbenligiray]

Is this still relevant @bdrhn9 ? (asking you because of the Nodary RNG OIS)