Beta — may change; breaking changes are coordinated with affected
customers. Suitable for evaluation, not production reliance.

Returns the service dependency graph for a time window: the services
observed and the calls between them, always scoped to a single
environment (required). Which graph you get depends on the identity
parameters you add on top of environment:

• environment only: the full graph for that environment.
• + serviceName: the graph centered on one service.
• + serviceName + endpointName: centered on one endpoint of that
  service.

services lists every service in the graph; invocations lists the
calls between them, each from a source to a target with aggregated
request, error, and latency metrics. A service that is never the
target of a call is a root.

When centered on an endpoint, endpointName is set on whichever side of
a call is that endpoint — source when the endpoint makes the call,
target when it serves the call — and is null on every other
participant. Match it exactly against the value from a prior response.

By default the full graph for the scope is returned. Set
directNeighborsOnly=true (with a serviceName) to return only the
focal service and the services one hop away from it. If a full graph is
not available for a request, it is rejected with BadRequest indicating
directNeighborsOnly=true should be used.

serviceNamespace is an optional additional filter that matches on
either end of a call (a call is kept when its source or target is in
that namespace — a cross-namespace union). environment, by contrast,
matches on both ends: a call is kept only when both its source and
target are in that environment.

Required parameter combinations: environment is always required (400 RequiredParamMissing otherwise); endpointName and
directNeighborsOnly each require a serviceName.

The graph is returned in a single response and is not paginated. A
request whose graph would exceed the maximum size is rejected with 413 PayloadTooLarge rather than truncated. Narrow the time window, or
center the graph on a service or endpoint, to reduce its size.