[Idea] - scrap tenant resolver middleware

Just an idea that I ended up implementing recently myself and seemed to work quite well. Consider this middleware: https://github.com/saaskit/saaskit/blob/master/src/SaasKit.Multitenancy/Internal/TenantResolutionMiddleware.cs

You can scrap this middleware entirely if:

1. Replace it with a “scoped” service, that does exactly what the middleware does, but in a Lazy<TTenant> such that the tenant is lazily resolved on first access of the Tenant property / method.

I think this then simplifies things a bit because:

1. TenantResolutionMiddleware can be dropped meaning less step for consumer.
2. People can inject the ITenantAccessor service whenever they need to access current Tenant (rather than inject TenantContext or TTenant.
3. You can change the implementation of ITenantAccessor so that it doesn’t need to store the TenantContext in httpcontext - because its already a scoped service, it can just keep the TenantContext directly as a property. This means you could also remove the extensions methods for httpcontext that Get / Set the TenantContext from httpcontext - as it would no longer be stored there - it would be held on the ITenantAccessor, which unlike the middleware, is accessible anywhere the tenant needs to be accessed.

[benfoster]

@dazinator I’m in the process of upgrading SaasKit to csproj and then will look at some of the items we discussed. It would be good if we could incorporate your ideas into SaasKit - I’ll have a look through your code tomorrow.

[dazinator]

Inject Task<TTenant> seems to work nicely: https://github.com/dazinator/Dotnettency/commit/a15eaa05566abe7efdef1e3468974da88869fee9#diff-dcaa3e511ec5996c9946ae81b027c8d1R16