[GTFS-Fares v2] Add duration limit to Fare Leg Join Rules and clarify…

[skalexch]

Summary

Describe the Problem

Use Cases

Proposed Solution

Type of change

GTFS Schedule

• Functional Change
• Non-Functional Change
• Documentation Maintenance

GTFS Realtime

• Specification Change
• Specification Change (Experimental Field)

Additional Information

Proposed Discussion Period

Testing Details

• Consumer(s):
• Producer(s):
• Estimated Testing Period:

Proposal Update Tracker

Date	Update Description
(YYYY-MM-DD)	(Brief description of the update)

Checklist

• I have read and understood the GTFS Change process.
• I have read and understood the GTFS Guiding Principles.
• I understand the Role of Advocate and the Responsibilities attached to it.
• I have signed the Contributor License Agreement (CLA).
• I have ensured that this proposal is not covered by an existing Pull Request.