Fix duration parsing error handling

[vpaturet]

Summary

A request that specifies a time penalty with an incorrect duration format:

accessEgressPenalty: [{
      streetMode: flexible
      timePenalty: "600ss + 1.3 t"
      costFactor: 1.3
    }],

fails with an HTTP 500 error:

"Text cannot be parsed to a Duration: '600ss' java.time.format.DateTimeParseException: Text cannot be parsed to a Duration: '600ss'
	at org.opentripplanner.framework.time.DurationUtils.duration(DurationUtils.java:121)
	at org.opentripplanner.routing.api.request.framework.LinearFunctionSerialization.parse(LinearFunctionSerialization.java:68)
	at org.opentripplanner.apis.transmodel.model.scalars.DoubleFunctionFactory$1.parseValue(DoubleFunctionFactory.java:59)
	at org.opentripplanner.apis.transmodel.model.scalars.DoubleFunctionFactory$1.parseLiteral(DoubleFunctionFactory.java:73)
	at org.opentripplanner.apis.transmodel.model.scalars.DoubleFunctionFactory$1.parseLiteral(DoubleFunctionFactory.java:40)

This PR fixes exception handling so that the parsing error is reported as a client error:

{
  "errors": [
    {
      "message": "Unable to parse duration: '600ss'",
      "locations": [],
      "extensions": {
        "classification": "BadRequestError"
      }
    }
  ]
}

Note: the parsing logic is moved to a private method LinearFunctionSerialization.parseDecimalSecondsOrDuration(). This method should probably not be promoted to the class DurationUtils: it is used solely to fix a backward compatibility issue (see #5304).

Issue

No

Documentation

No

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.46%. Comparing base (2a5c8be) to head (4c5d1ea).
Report is 8 commits behind head on dev-2.x.

Additional details and impacted files

@@            Coverage Diff             @@
##             dev-2.x    #5947   +/-   ##
==========================================
  Coverage      69.45%   69.46%           
- Complexity     17070    17076    +6     
==========================================
  Files           1937     1937           
  Lines          73692    73714   +22     
  Branches        7540     7543    +3     
==========================================
+ Hits           51184    51202   +18     
- Misses         19880    19882    +2     
- Partials        2628     2630    +2     

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[leonardehrenfried]

Is it possible to write a test for this behaviour?

[vpaturet]

I've added a couple of test cases to test the behavior with decimal seconds.
I see now that the corner case with invalid duration was not covered, so I added a test case for this as well.