docs: add README; chore: SPDX license, silence build warnings

Author: nyorf

README.md

@@ -0,0 +1,93 @@
+# wisepay-observability
+
+Shared structured-logging + tracing library for wisepay services. It ships JSON
+log records to OpenSearch (with a console fallback), and propagates W3C trace
+context across services so logs can be correlated by `trace_id`.
+
+Consumed by `ym-api`, `iris`, `currency-exchange-rates-api`, `tg-bot`,
+`currency-exchange-rates-parsers` and `banking`.
+
+## Install
+
+Pinned by tag (this is the supported install path — every release also attaches
+a built wheel + sdist):
+
+```
+wisepay-observability @ git+https://github.com/wisepayru/observability.git@1.1.1
+```
+
+Requires Python >= 3.14.
+
+## Quickstart
+
+### HTTP service (FastAPI / Starlette)
+
+```python
+from fastapi import FastAPI
+from observability import setup_logging, TraceMiddleware
+
+setup_logging()                  # configure root logging from the environment
+app = FastAPI()
+app.add_middleware(TraceMiddleware)
+```
+
+`TraceMiddleware` starts (or continues, from an inbound `traceparent`) a trace
+per request, stores `trace_id`/`span_id` in context so every log record carries
+them, logs one record per request with **sanitized** headers (secrets like
+`authorization` / `cookie` / `x-api-key` redacted), and sets a `traceparent`
+response header.
+
+### Outgoing calls — propagate the trace
+
+```python
+import httpx
+from observability import build_outgoing_headers
+
+async with httpx.AsyncClient() as client:
+    await client.get(url, headers=build_outgoing_headers())
+```
+
+### Scripts / workers / bots
+
+```python
+from observability import setup_logging, run_context
+
+setup_logging()
+with run_context("nightly-rates"):
+    fetch_and_store_rates()      # every log inside carries the run's trace_id
+```
+
+`interaction_context` is an alias of `run_context` (used by `tg-bot`).
+
+## Configuration
+
+`setup_logging()` reads everything from the environment:
+
+| Variable | Default | Purpose |
+|---|---|---|
+| `OPENSEARCH_HOST` | _(unset)_ | OpenSearch node URL. **If unset (or no password), logs go to the console** instead of OpenSearch. |
+| `OPENSEARCH_PASSWORD` | _(unset)_ | Basic-auth password; required (with host) to enable the OpenSearch handler. |
+| `OPENSEARCH_USER` | `admin` | Basic-auth username. |
+| `OPENSEARCH_INDEX` | `wisepay-logs` | Target index. Services set this per app, e.g. `wisepay-ym-api`. |
+| `SERVICE_NAME` | `wisepay-service` | Emitted as `service` on every record. |
+| `APP_ENV` | `production` | Emitted as `env`. |
+| `LOG_LEVEL` | `DEBUG` | Root log level. |
+| `LOG_BATCH_SIZE` | `50` | Records per bulk flush. |
+| `LOG_FLUSH_INTERVAL` | `1.0` | Seconds between flushes. |
+| `LOG_MAX_QUEUE_SIZE` | `10000` | In-memory queue cap (overflow falls back to stderr). |
+
+Business logs ship to OpenSearch **or** the console, not both. App code can
+attach arbitrary fields via `extra=` (e.g. `correlation_id`, `order_id`) and
+they pass through to the document untouched.
+
+## Development
+
+```bash
+python3.14 -m venv .venv
+.venv/bin/pip install -e . -r requirements-test.txt
+.venv/bin/ruff check .
+.venv/bin/pytest
+```
+
+See [`tests/README.md`](tests/README.md) for the test layout and
+[`docs/release.md`](docs/release.md) for the versioning + release flow.

pyproject.toml

@@ -1,12 +1,12 @@
 [build-system]
-requires = ["setuptools>=68", "setuptools-scm>=8"]
+requires = ["setuptools>=77", "setuptools-scm>=8"]
 build-backend = "setuptools.build_meta"
 
 [project]
 name = "wisepay-observability"
 description = "Shared OpenSearch/OTEL structured logging for wisepay services"
 requires-python = ">=3.14"
-license = { text = "MPL-2.0" }
+license = "MPL-2.0"
 dynamic = ["version"]
 dependencies = [
     "opentelemetry-api",