fix: emit required array for non-nullable action parameters in requestBody

[axherrm]

Fixes #354

Problem

pathItemAction built the requestBody schema with a properties object
for every non-binding parameter but never emitted a required array.
As a result, downstream OpenAPI consumers (validators, code generators,
LLM-based agents) treated all action parameters as optional, even when
Nullable="false" was set — causing the service to return 400 Bad Request
when those parameters were omitted.

OData 4.01 Protocol §11.5.5.1 states that non-binding parameters that are
neither nullable nor annotated with Core.OptionalParameter must be
supplied in the request body. The generated OpenAPI document should reflect
this constraint.

Fix

In pathItemAction, collect the names of parameters where $Nullable is
not true and @Core.OptionalParameter is not set, then emit them as
required on the requestBody schema object. This mirrors the logic already
present in pathItemFunction for URL parameters (line 1720).

Changes

• lib/csdl2openapi.js — pathItemAction: compute and conditionally
  emit required array on the requestBody schema.
• test/csdl2openapi.test.js — new test case
  "action with nullable and not nullable parameters" covering all four
  combinations: non-nullable (required), typed non-nullable (required),
  $Nullable: true (not required), and @Core.OptionalParameter (not
  required).
• test/annotations.test.js — updated "Default Namespace" snapshot to
  include the now-emitted required array.
• examples/TripPin.openapi3.json — updated ShareTrip action
  requestBody (userName, tripId are both Nullable="false").
• examples/odata-rw-v3.openapi3.json — updated Discount and
  IncreaseSalaries action requestBodies (single non-nullable parameter
  each).

[HeikoTheissen]

This makes collection-valued parameters required, although OData-Protocol, section 11.5.6.1 allows their omission.

The interpretation of an omitted non-binding collection-valued parameter is up to the service regardless of its nullability or optionality.

Note also the failed test.

[axherrm]

thank you for the comment - does the fix I added resolve the issue?

Also, I commited the openapi artifacts after test run so that they should have no diff in CI/CD (diff was the required array which is new and needs to be added to the artifacts to my understanding). Can you permit a new CI/CD run