Description of Identifier rules wrong in documentation

[ClemensLinnhoff]

Describe the bug

This is the definition of the Identifier in the documentation:

Has to be unique among all simulated items at any given time. For ground truth, the identifier of an item (object, lane, sign, etc.) must remain stable over its lifetime. Identifier values may be only be reused if the available address space is exhausted and the specific values have not been in use for several time steps. Sensor specific tracking IDs have no restrictions and should behave according to the sensor specifications.

It says, that every ID shall be globally unique except for sensor specific tracking IDs. This does not make much sense. A sensor ID is completely independent from object IDs or route IDs. Furthermore, sensor IDs depend on the sensor setup and are independent from the scenario, where the object IDs are defined. Same with the route IDs: They are defined in the map and are independent from sensor setup and scenario.

Describe the expected behavior

I propose:

• Set rule is_globally_unique in all fields that are actually supposed to be globally unique (NOT sensor ID or tracking ID for example).
• Change description of Identifier to state that the ID is only globally unique, if specified by the rule is_globally_unique.
• Optional: Introduce new rule is_unique to specify uniqueness within the individual field

[jdsika]

Introducing a new rule can be introduced in v3.7.1