Context:
The special "external" sub-path should only be used on share pages and from there any new links shall not include this sub-path.

AT:

• "Open in Optimize"-Links must be cleaned from a potential `/external` sub-path that was introduced with OPT-4803 & OPT-4807 for the:
  • report share page
  • dashboard share page
• this must be backwards-compatible with old share links that don't include the `/external` sub-path:
  expected "Open in Optimize"-Link for the following both cases: https://stage.optimize.camunda.cloud/#/report/b443f40b-1b0e-42e6-a1e5-257a20b3a741
  • old link: https://stage.optimize.camunda.cloud/#/share/report/b443f40b-1b0e-42e6-a1e5-257a20b3a741 => no removal of "/external" needed
  • new link: https://stage.optimize.camunda.cloud/external/#/share/report/b443f40b-1b0e-42e6-a1e5-257a20b3a741 => "/external" needs to get replaced when generating the "Open in Optimize"-Link