[moetemp]

What changed?

This PR adds a stream-service sample for Python and TypeScript, with today's output. #272 adds .NET with its fix. It has a stream resource built from a ref, create-stream, append, read, describe and close, with 64-bit offsets, payloads and durations.

Its records are proto-backed, as a stream service's are. Upstream has no stream protos, so the sample has its own small proto in descriptors/streamsample/v1/, with checked-in bindings. The samples README has the commands that regenerate them. build_examples now loads every *.bin under descriptors/.

Why?

Later fixes show their effect as a golden diff on this sample.

How did you test it?

The goldens. A TypeScript test sends a full ReadRecordsRequest through the converter, so the TypeScript type file can't drift from the proto.

What comes next

These fixes are ready, in this order. Each one adds its shape to this sample, then the fix.

• fix(dotnet): keep a resource property apart from its class name #272: adds .NET, where the stream field of the Stream class fails with CS0542, then the fix.
• moetemp/nexgen#52: Check required resource fields of a response. Adds create-stream returning the stream resource.
• moetemp/nexgen#56: Allow a result record to hold a resource. Adds a create-stream-result holder record.
• moetemp/nexgen#53: Emit @nexus.doc on resources and methods as Python docstrings.
• moetemp/nexgen#70: Convert 64-bit resource method values to Long for a proto request in TypeScript. Adds 64-bit method parameters. Needs fix(wit): keep the size and sign of WIT integers #265.
• moetemp/nexgen#54: Generate a Python caller per service over a transport. Turns on the client for the sample.
• moetemp/nexgen#55: Add @nexus.long-poll to the Python caller. Marks read-records as a long poll.
• moetemp/nexgen#57: Add Python client classes for resources with methods.
• moetemp/nexgen#71: Drop the bare keyword marker from a Python signature with no parameters. Adds a stream-writer interface with no endpoint.
• moetemp/nexgen#60: Indent the docstrings of Python caller methods. Adds a doc on a writer operation.
• moetemp/nexgen#69: Import record types that an endpoint-less Python client uses in unpacked parameters. Adds open-writer.
• moetemp/nexgen#72: Plan proto unsigned integers as unsigned. Adds a uint64 writer id.
• moetemp/nexgen#73: Build a returned proto-wire resource in an endpoint-less TypeScript client. Makes open-writer return the writer resource.

#262 adds a status enum to the holder record once it merges.