Change Transmodel API path to /otp/transmodel/v3

[leonardehrenfried]

Summary

This PR changes the path of the Transmodel API to /otp/transmodel/v3. In line with others it is totally backwards-compatible and you can keep using the old path for the time being.

In line with @t2gran's suggestion the endpoint at /otp/routers/default/transmodel/live has been removed as it simplified the migration of this path a lot.

Issue

#4052

Documentation

Updated.

[codecov]

Codecov Report

Attention: 47 lines in your changes are missing coverage. Please review.

Comparison is base (4e4af20) 67.50% compared to head (6d07809) 67.46%.
Report is 6 commits behind head on dev-2.x.

Files	Patch %	Lines
...xt/reportapi/model/TransitGroupPriorityReport.java	0.00%	39 Missing ⚠️
...planner/ext/reportapi/resource/ReportResource.java	0.00%	4 Missing ⚠️
...opentripplanner/apis/transmodel/TransmodelAPI.java	0.00%	3 Missing ⚠️
...in/java/org/opentripplanner/apis/APIEndpoints.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             dev-2.x    #5637      +/-   ##
=============================================
- Coverage      67.50%   67.46%   -0.05%     
+ Complexity     16285    16284       -1     
=============================================
  Files           1888     1889       +1     
  Lines          71547    71591      +44     
  Branches        7408     7412       +4     
=============================================
- Hits           48301    48300       -1     
- Misses         20747    20791      +44     
- Partials        2499     2500       +1     

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[habrahamsson-skanetrafiken]

LGTM