Remove mongodb

[rem1niscence]

Remove all references of mongodb to only keep the postgres db as the only source of truth. This is done by

• Removing anywhere where mongo was used
• Removing fallback code from phd
• Modify all tests that needed to have some data from a db to use a HTTP mock to retrieve PHD results
• Add a small function to phd to return HTTP error objects in case the HTTP call fails

Although I tried my best to not modify any logic, a small change had to be done to the loadBlockchains function to return the expected Error response, besides that no other change was made to any logic

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[commoddity]

These changes all look good to me. Thanks man.

[adshmh]

Why is this needed here? Doesn't this happen after each test case already with the added code?

[rem1niscence]

yes and that's exactly why I put it there, to remove the blockchain response so it returns 404 and mimics the not found test