feat: admin APIs for token authenticated registration (#3101)

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Signed-off-by: `Santhoshivan Amudhan santhoshivan23@gmail.com`

clientapi/api/api.go

@@ -21,3 +21,11 @@ type ExtraPublicRoomsProvider interface {
 	// Rooms returns the extra rooms. This is called on-demand by clients, so cache appropriately.
 	Rooms() []fclient.PublicRoom
 }
+
+type RegistrationToken struct {
+	Token       *string `json:"token"`
+	UsesAllowed *int32  `json:"uses_allowed"`
+	Pending     *int32  `json:"pending"`
+	Completed   *int32  `json:"completed"`
+	ExpiryTime  *int64  `json:"expiry_time"`
+}