[api] using io.WriteString for writing responses instead of http.ResponseWriter.Write(...)

[ryandeivert]

to: @securityclippy
size: small

Changes

• Now using io.WriteString to write http responses due to part of an answer found here:

  All in all, whenever you write string values, [it's] recommended to use io.WriteString() as it may be more efficient (faster).

• Also updating how unexpected errors are reported to the user by using http.Error instead of attempting to write a custom error struct.

[mattjane-okta]

@ryandeivert is there ever an instance when the content-type would not be json? Generally we want to try to make everything a json response, but if there's a use-case for non-json let me know. (the whole point being, why not set the header type once, no matter what)

[ryandeivert]

Purposely, probably not :) the only time (by design) I think the content type will be anything other than json is if http.Error is called - but that would overwrite the json content type if it existed already. I'll make the change 👍