add update queues for SCUs

[panentheos]

Summary of changes

Asana Ticket: RTS: Support communication with new SCU app

Adds new processes for communicating with SCUs. Each SCU gets its own independent queue, using GenStage to simplify queueing and message passing. Expects to receive a new environment variable containing the mapping from SCU id to ip address, which will be provided separately.

Note that while this does add the processes themselves, they don't currently do anything because nothing is trying to call out to the new SCU app.

[github-actions]

Coverage of commit 5929e1f

Summary coverage rate:
  lines......: 71.3% (1828 of 2563 lines)
  functions..: 74.6% (513 of 688 functions)
  branches...: no data found

Files changed coverage rate:
                                                             |Lines       |Functions  |Branches    
  Filename                                                   |Rate     Num|Rate    Num|Rate     Num
  =================================================================================================
  lib/pa_ess/scu_queue.ex                                    |66.7%      6|66.7%     6|    -      0
  lib/pa_ess/scu_updater.ex                                  | 7.1%     28|40.0%     5|    -      0
  lib/realtime_signs.ex                                      | 100%     15| 100%     3|    -      0
  lib/signs/utilities/signs_config.ex                        |95.5%     22|83.3%     6|    -      0

Download coverage report

[PaulJKim]

Just curious, why do we need to send the scu_id to Signs UI as a header?

[panentheos]

This endpoint doesn't exist yet, but Signs UI will need this in order to attribute the data to the right sign, since the payload itself is not sufficient to differentiate it globally.