api: Convert timezones before txn query

[Eric-Warehime]

Summary

Fixes #458

Test Plan

Added unit tests.

[shiqizng]

also add a test in handler to validate this works.
https://github.com/algorand/indexer/blob/develop/api/handlers_test.go#L80-L82

[codecov]

Codecov Report

Merging #1543 (b3d50f8) into develop (5c1a24c) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #1543      +/-   ##
===========================================
+ Coverage    68.20%   68.34%   +0.14%     
===========================================
  Files           38       38              
  Lines         7438     7440       +2     
===========================================
+ Hits          5073     5085      +12     
+ Misses        1934     1926       -8     
+ Partials       431      429       -2     

Impacted Files	Coverage Δ
idb/postgres/postgres.go	67.28% <100.00%> (+0.48%)	⬆️

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[tzaffi]

also add a test in handler to validate this works. https://github.com/algorand/indexer/blob/develop/api/handlers_test.go#L80-L82

I echo this sentiment. We can see that previously the coverage was lacking as all the Before/AfterTimes were UTC. So we ought to be able to add a test case that failed previously and is now fixed thanks to this PR.

[tzaffi]

LGTM. Optionally, it would be great to change or add one of the cases in handlers_test.go to be non-UTC

[Eric-Warehime]

@shiqizng @tzaffi
With this implementation we can't add a handlers test because I haven't changed the idb.TransactionFilter. It seems like at the handlers level we would assume that the idb implementation would properly handle any time.Time objects regardless of their timezone. So instead of converting all idb filter objects to have UTC timezone, I've changed it in the postgres implementation itself.

So the handlers output would be unchanged, but when you get the resulting sql query for postgres it would go from idb.TransactionFilter{BeforeTime: Non-UTC-TIME} to something like SELECT...ON...WHERE h.realtime > UTC-Converted-Time

[tzaffi]

@shiqizng @tzaffi With this implementation we can't add a handlers test because I haven't changed the idb.TransactionFilter. It seems like at the handlers level we would assume that the idb implementation would properly handle any time.Time objects regardless of their timezone. So instead of converting all idb filter objects to have UTC timezone, I've changed it in the postgres implementation itself.

So the handlers output would be unchanged, but when you get the resulting sql query for postgres it would go from idb.TransactionFilter{BeforeTime: Non-UTC-TIME} to something like SELECT...ON...WHERE h.realtime > UTC-Converted-Time

I wonder if the fixtures test is a good place to add this. I'm not proposing to add it to this PR because the transactions/ endpoint isn't yet implemented for the fixtures (though it's pretty easy to add it). I can create a small issue to add such a test case if others agree.

[shiqizng]

the existing tests are missing cases for idb.TransactionFilter{BeforeTime: Non-UTC-TIME} though. The handler output should change, right? we want prove query provided in 458 now returns the correct results?

[shiqizng]

typo.