Handle errors gracefully on routes

[isinyaaa]

Description

This fixes an unhandled error on the GetEnvironmentEnvironments route, as well as standardizes error value treatment using an error to http status converter. All status codes now use the standard net/http consts (enum).

How Has This Been Tested?

Tested with make test.

Merge criteria:

• The commits and have meaningful messages; the author will squash them after approval or will ask to merge with squash.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[tarilabs]

thank you @isinyaaa for this PR,
let me know if the comment below you want to do it as part of this PR or future PR

[rareddy]

Do we want to do anything with left over "todo" comments? if no further steps we are going to like 401 ones which get intercepted at filter level, can we remove them?

[tarilabs]

Do we want to do anything with left over "todo" comments? if no further steps we are going to like 401 ones which get intercepted at filter level, can we remove them?

I'd advise to manage the TODOs as follow-up PR, so to keep the scope of this PR to start consolidating repeated code, while "debt" to be managed separately

[tarilabs]

looks good to me @isinyaaa thank you for the quick loop, I'd say we merge this and we track the TODO for the auth in a single filter in a subsequent PR; reason is I would like to parallelize work since a reported issue (#95 ) could then investigated in parallel better with this one merged already so we set a baseline

/lgtm
/approve

[google-oss-prow]

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This pull-request has been approved by: tarilabs

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