Making Multiple developer portals work with 1 Application Gateway and 1 Management certificate

[olivierblazevic6]

Hello,

I've been using the self-hosted developer portal for one APIM, which is in Internal VNET mode, and it works wonderfully.

Now, I'd like to expand this developer portal to all my APIMs (5 total). but I'm facing a problem.
Having only one certificate for all the APIMs, I need to find a way to redirect all calls made to the management endpoints to each APIM.

I was thinking of using the rules and Rewrite sets the Application Gateway offers, since I'm already using it succesfully on the Gateway endpoint of the APIMs, and thus, applying it to the management endpoint.

The way it is used on the gateway endpoint is as follows :
Calls are made on a URL (for example "https://{gateway_url_here}/{environment}/{API_details_path}), and the App gateway reads the {environment} part, redirects it to the good backend pool while also removing the {environment} particle, leaving only "https://{gateway_url_here}/{API_details_path}" to be read.
Thus, each APIM reads only the calls it is supposed to answer.

Now, onto the developer portal issue :

What I wanted to do, was to modify the config files (namely config.runtime.json, config.design.json and config.publish.json) to include, for each APIM, a specific marker (just like the {environment} particle in the aforementioned example) that would allow the app gateway to redirect each demand to the appropriate backend pool

For example :

Putting theory to action, I modified each of the three files previously listed, and only got 500 on my calls after publishing.
Then I also tried modifying every single instance of a developer or management URL in all the repo's files, but I got the same result.

I was wondering if someone had any idea as to what I should be modifying, or if my plan is even remotely feasible (seeing it works nicely with the gateway endpoint, I do not see any reasons why it shouldn't work here)

I already tried contacting the Microsoft support, but I think I bored them and they gave me no real reasons as to why my project can't be working.

To anyone reading or willing to help, thanks in advance !