Multiple identical endpoints are allowed

Consider an example:

**/bar:**
&nbsp;&nbsp;&nbsp;&nbsp;**/foo:**
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;description: Endpoint /bar/foo
**/bar/foo:**
&nbsp;&nbsp;&nbsp;&nbsp;description: second endpoint /bar/foo

It results in generating two endpoint nodes with identical URIs.

Coexistence of such twin endpoints should be disallowed.
