Q: Identityserver4 with multiple (custom) user stores We're designing a green field multitenant (web/mobile) system, and plan to use IdentityServer4.
I lieu of first-class multitenant support in IdentityServer4 we're looking into having separate user stores per tenant. When trying to figure out how to go about doing this, I've looked at the implementation of https://github.com/IdentityServer/IdentityServer4.AspNetIdentity
It appears to be registering an implementation of IResourceOwnerPasswordValidator, which only is called when using the 'Resource owner password' grant type. 
Which interfaces should be implemented and registered to support custom/multiple user stores in the other (e.g. implicit) grant types?
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Thor A. Johansen

A: Interactive login logic goes into the "account controller". You can use the acr_values parameter (or some custom parameter) to indicate the tenant ID from the client and then retrieve that in the controller via the IIdentityServerInteractionService.GetAuthorizationContext method.
