Modifies graph API to not start graph monitoring process if no UserEquipment nodes are found in the graph

Implements a DELETE API endpoint for stopping a graph monitoring process and refactors the graph API tests

Updates graph_monitor API endpoint to also save the request identifier and the pipeline process identifier

Implements and tests an addition to the response of the build request for a temporal graph - now the list of endpoints is also returned

Adds API endpoint to continuously execute the graph workflow - implements error handling functionality only

Refactors tests for handling invalid requests and adds new tests for the execute pipeline API endpoint

Updates graph build API endpoint - timestamps are now passed in the JSON body and not in the URL query string