Move from Azure Functions Proxies to API Management

Azure Functions Proxies will be deprecated on 30 September 2025, so this solution needs to move to use APIM.

From the support mail:

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## Community support for Azure Functions Proxies ends on 30 September 2025

**You're receiving this email because you're using Azure Functions Proxies. If you have already migrated off of Proxies, no action is required from you at this time.**
Azure API Management is Microsoft's solution to securely create and manage modern APIs at scale. Azure Functions Proxies are a very limited subset of these capabilities that will no longer be invested in to avoid duplication of functionality. Azure Functions Proxies will continue to remain in maintenance mode until 30 September 2025 after which it'll no longer be supported.

### Required action

Please review the [migration guidance](https://aka.ms/proxydeprecation) and transition to Azure API Management as soon as possible to avoid disruption to your Function applications using Proxies.
Azure API Management provides the same functionality as Functions Proxies as well as advanced tools for building and maintaining APIs such as OpenAPI integration, rate limiting and exhaustive policy support.
To enable seamless upgrade of Function applications to runtime V4.x, we'll be adding Proxy support back in Functions runtime V4.x by October 2022. However, migrating away from Proxies is strongly recommended.

Start with the linked Azure Functions Proxies migration guidance and inspect this repository's Azure deployment configuration to locate the proxy definitions. Done means the solution uses Azure API Management instead of Functions Proxies, with equivalent routing preserved; the issue names no files or tests to run.

Written by the indexing model from the issue text.