feat: Add initial AuthzQuerier implementation (#5919)

feat: Add initial AuthzQuerier implementation
- Adds package database/dbauthz that adds a database.Store implementation where each method goes through AuthZ checks
- Implements all database.Store methods on AuthzQuerier
- Updates and fixes unit tests where required
- Updates coderd initialization to use AuthzQuerier if codersdk.ExperimentAuthzQuerier is enabled

coderd/httpmw/authz.go

@@ -0,0 +1,37 @@
+package httpmw
+
+import (
+	"net/http"
+
+	"github.com/coder/coder/coderd/database/dbauthz"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// AsAuthzSystem is a chained handler that temporarily sets the dbauthz context
+// to System for the inner handlers, and resets the context afterwards.
+//
+// TODO: Refactor the middleware functions to not require this.
+// This is a bit of a kludge for now as some middleware functions require
+// usage as a system user in some cases, but not all cases. To avoid large
+// refactors, we use this middleware to temporarily set the context to a system.
+func AsAuthzSystem(mws ...func(http.Handler) http.Handler) func(http.Handler) http.Handler {
+	chain := chi.Chain(mws...)
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+			ctx := r.Context()
+			before, beforeExists := dbauthz.ActorFromContext(r.Context())
+			if !beforeExists {
+				// AsRemoveActor will actually remove the actor from the context.
+				before = dbauthz.AsRemoveActor
+			}
+
+			// nolint:gocritic // AsAuthzSystem needs to do this.
+			r = r.WithContext(dbauthz.AsSystem(ctx))
+			chain.Handler(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+				r = r.WithContext(dbauthz.As(r.Context(), before))
+				next.ServeHTTP(rw, r)
+			})).ServeHTTP(rw, r)
+		})
+	}
+}