BNF data is moving from NHS BSA's ISP to ODP

Why are we doing this?

We currently manually download BNF coding system updates from the NHS BSA Information Services Portal and import them.

BNF data is now available from the NHS BSA Open Data Portal.

"in the coming months" the BNF data will no longer be available from the ISP:

We should update our processes to get the data from the ODP, preferably via its API, and preferably getting the monthly updates when these become available.

Requested in Slack thread.

How will we know when it's done?

We are regularly updating the BNF coding system on OpenCodelists from the NHS BSA ODP.

What are we doing?

• Assess any changes in the data provided for the BNF between that from the ISP and the ODP (https://github.com/opensafely-core/opencodelists/issues/3010#issuecomment-5048314067, see also comments on this issue)
• If necessary, implement changes to the BNF coding system's import_data.py to reflect these (#3167)
• Writing an API client for the ODP API (optional as we could still do this manually) (potentially in #3168)
• Schedule loading of the BNF data from the API (if we end up using the API) (potentially in #3168)

Defining delivery tasks guidance