Add the option to the API to configure CORS. (#267)

* Add the option to the API to configure CORS.

* Update api/README.md

Co-authored-by: Lukas Phaf <lukas.phaf@knmi.nl>

* Change middleware order and remove arguments with defaults.

* Update readme with headers environment variable.

* Ensure empty list.

* Reorder according to https://fastapi.tiangolo.com/tutorial/middleware/#multiple-middleware-execution-order.

---------

Co-authored-by: Lukas Phaf <lukas.phaf@knmi.nl>

Author: Jeffrey-Vervoort-KNMI

api/README.md

@@ -1,28 +1,30 @@
 # E-SOH API
 
-## Enviorment variable
-These enviorment variables should be set when you are starting the container or be set in the enviorment where you are running the application.
-### DSHOST
+## Environment variables
 
-IP address to datastore
+Environment variables that can be used to configure the container or the environment where you are running the application.
 
-### DSPORT
-
-Port the datastore is available on.
-
-### FORWARDED_ALLOW_IPS
-
-Environment variable used to set the `forwarded-allow-ips` in gunicorn. If this API is set behind a proxy, `FORWARDED_ALLOW_IPS` should be set to the proxy IP. Setting this to `*` is possible, but should only be set if you have ensured the API is only reachable from the proxy, and not directly from the internet. If not using docker compose this have to be passed to docker using the `-e` argument.
+| Name                | Description                                                                                                                   | Mandatory |
+|---------------------|-------------------------------------------------------------------------------------------------------------------------------|-----------|
+| DSHOST              | Address to the datastore                                                                                                      | ☑         |
+| DSPORT              | Port where the datastore is available.                                                                                        | ☑         |
+| FORWARDED_ALLOW_IPS | Environment variable used to set the `forwarded-allow-ips` in gunicorn. If this API is set behind a proxy, `FORWARDED_ALLOW_IPS` should be set to the proxy IP. Setting this to `*` is possible, but should only be set if you have ensured the API is only reachable from the proxy, and not directly from the internet. If not using docker compose this have to be passed to docker using the `-e` argument. | ☑         |
+| GUNICORN_CMD_ARGS   | Command-line arguments for configuring Gunicorn, a Python WSGI HTTP Server.                                                   | ☐         |
+| CORS_ORIGINS        | Indicates whether the response can be shared with requesting code from the given origins (passed as a comma separated string) | ☐         |
+| CORS_HEADERS        | Indicates what headers should be supported with cross-origin requests (passed as a comma separated string)                    | ☐         |
 
 ## Prerequisites of running locally
 
 ### QUDT
+
 Move the `std_unit_names.json`to the api folder with
+
 ```bash
 just copy-units
 ```
 
 Generate the file needed for QUDT dictionary by running
+
 ```bash
 python generate_qudt_units.py
 ```

api/main.py

@@ -17,6 +17,7 @@
 from routers import edr
 from routers import feature
 from utilities import create_url_from_request
+from fastapi.middleware.cors import CORSMiddleware
 
 
 all_collections = collections_metadata.keys()
@@ -40,7 +41,15 @@ def setup_logging():
     root_path=os.getenv("FASTAPI_ROOT_PATH", ""),
     **openapi_metadata,
 )
+
 app.add_middleware(BrotliMiddleware)
+if (cors_origins := os.getenv("CORS_ORIGINS", None)) is not None:
+    cors_headers = os.getenv("CORS_HEADERS", None)
+    app.add_middleware(
+        CORSMiddleware,
+        allow_origins=cors_origins.split(","),
+        allow_headers=[] if cors_headers is None else cors_headers.split(","),
+    )
 add_metrics(app)