test(gateway): slight refactor of some presentation and add some endpoint registration tests

[ramin]

goals: readability, test coverage

Appreciate that the gateway is v unimportant but is exists. I was starting at the top just looking for places to give a clean up and add some unit test coverage and found this.

Mostly trying to make it cleaner to read, then added some tests, also wanted to add a /status/health endpoint just for ease, i would want this as a node operator if i was running with --gateway for whatever reason

Also took liberty to take some error handling code out of writeError that would never execute. In trying to write a test to trigger the json.Marshal error case, i realized that as err.Error() always returns a string it could never trigger json.Unmarshal to fail without panic before even getting there, so removed that code path.

i might revisit this and give it another refactor at some point soon, unless we're planning to remove this completely?

on to next area

[codecov-commenter]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (b487830) 51.00% compared to head (fcd43a0) 51.69%.

Files	Patch %	Lines
api/gateway/health.go	0.00%	7 Missing ⚠️
api/gateway/util.go	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2939      +/-   ##
==========================================
+ Coverage   51.00%   51.69%   +0.69%     
==========================================
  Files         177      178       +1     
  Lines       11147    11196      +49     
==========================================
+ Hits         5685     5788     +103     
+ Misses       4959     4909      -50     
+ Partials      503      499       -4     

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[distractedm1nd]

Looks good, glad we will have something on both gateway and rpc for health/readiness.

Talking with Jordan Oroshiba, health should be an endpoint that determines if the node is "healthy" ofc, but idrk what metrics we would use to determine this... hmm

[Wondertan]

idrk what metrics we would use to determine this... hmm

In our case it should be checking for deadlocks/stalls. E.g it would ask Syncer and DASer for their state and if they don't respond or change their state in a timeout then we make a conclusion that things aren't healthy. This is btw also why Ready check is not health check @ramin