Jimqueline/backend refactor first

[zijin1994]

First pass of backend refactor
followed this pattern:

1. move route logic into utils folder next to the route.
2. for non api call functions, they sit inside the utils.ts file in the utils folder.
3. if there are more than one type definitions, they go into a types.ts file next to the route, otherwise, they sit next to the function.

If we want to further refactor the code, start moving functions inside the utils functions near the route.

[jq-ln]

Looks good, works for me!