Revert "Revert "Determine emptier car location and crowding description""

[PaulJKim]

Reverts #684

Errors were occurring in Dev because the multi_carriage_details field is still only in dev-green and that was causing get_crowding_description to attempt to call Enum.map(nil).

Adding a default of [] to the parsing logic. Tested against the prod RTR feed to make sure there are no errors.

[github-actions]

Coverage of commit 8ee13fb

Summary coverage rate:
  lines......: 75.4% (1893 of 2512 lines)
  functions..: 76.9% (517 of 672 functions)
  branches...: no data found

Files changed coverage rate:
                                                             |Lines       |Functions  |Branches    
  Filename                                                   |Rate     Num|Rate    Num|Rate     Num
  =================================================================================================
  lib/content/audio/approaching.ex                           |70.4%     27| 100%     7|    -      0
  lib/content/audio/predictions.ex                           |94.2%     52| 100%     1|    -      0
  lib/content/audio/train_is_arriving.ex                     |48.4%     31| 100%     5|    -      0
  lib/content/message/predictions.ex                         |56.7%    120|66.7%    15|    -      0
  lib/engine/locations.ex                                    |61.4%     57|66.7%    15|    -      0

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[panentheos]

See comment, then looks good.

[panentheos]

nit: If we do location["vehicle"]["multi_carriage_details"] || [], we could remove the outer guard and map over it unconditionally, which might be a little cleaner.

[github-actions]

Coverage of commit 8ee13fb

Summary coverage rate:
  lines......: 75.3% (1891 of 2512 lines)
  functions..: 76.9% (517 of 672 functions)
  branches...: no data found

Files changed coverage rate:
                                                             |Lines       |Functions  |Branches    
  Filename                                                   |Rate     Num|Rate    Num|Rate     Num
  =================================================================================================
  lib/content/audio/approaching.ex                           |70.4%     27| 100%     7|    -      0
  lib/content/audio/predictions.ex                           |94.2%     52| 100%     1|    -      0
  lib/content/audio/train_is_arriving.ex                     |48.4%     31| 100%     5|    -      0
  lib/content/message/predictions.ex                         |56.7%    120|66.7%    15|    -      0
  lib/engine/locations.ex                                    |60.3%     58|66.7%    15|    -      0

Download coverage report

[github-actions]

Coverage of commit e898a47

Summary coverage rate:
  lines......: 75.3% (1891 of 2511 lines)
  functions..: 76.9% (517 of 672 functions)
  branches...: no data found

Files changed coverage rate:
                                                             |Lines       |Functions  |Branches    
  Filename                                                   |Rate     Num|Rate    Num|Rate     Num
  =================================================================================================
  lib/content/audio/approaching.ex                           |70.4%     27| 100%     7|    -      0
  lib/content/audio/predictions.ex                           |94.2%     52| 100%     1|    -      0
  lib/content/audio/train_is_arriving.ex                     |48.4%     31| 100%     5|    -      0
  lib/content/message/predictions.ex                         |56.7%    120|66.7%    15|    -      0
  lib/engine/locations.ex                                    |61.4%     57|66.7%    15|    -      0

Download coverage report