fixed the returned status codes

[interestIngc]

Description

Fixed status codes returned by the resource server in failure cases. Now we return 401 (Unauthorized) if authentication token is invalid and 500 (Internal error) if there happened any error non-related to the user's input, e.g. when encoding the server response into json. Previously 400 (Bad request) was returned in all the cases.

Test Cases Checklist

SECTION 1: RESOURCE SERVER (http://localhost:5001/)

• [x] http://localhost:5001/ home page loads
• [x] "LoginAsUser" button takes you to the user login page
• [x] Log in using "tester" and "12341234" should succeed
• [x] Updating the display name should work
• [x] Log out and Register a new user and try to log in with that new user
• [x] "LoginAsClient" button takes you to the client login page
• [x] Log in using "layer8" and "12341234" should work
• [x] You will be able to see your UID and Secret in profile
• [x] Log out and Register a new client and log in using that should work

SECTION 2: WE'VE GOT POEMS (http://localhost:5173/)

• [x] Log in with 'tester' / '1234'
• [x] Log in anonymously with Layer8
• [x] Clicking "Get Next Poem" loads different poem correctly x 3
• [x] Clicking "Logout" takes you to the login screen
• [x] Clicking "Register" takes you to the registration page
• [x] Registering with a username, password, and profile image is successful
• [x] Logging in with the new username / password succeeds
• [x] Logging in with Layer8 opens the pop-up
• [x] Logging in with the newly registered credentials from Section 1 succeeds
• [x] User chooses to share their new "Username" & "Country" from the Layer8 Resource Server
• [x] Clicking "Get Next Poem" loads different poem correctly x 3
• [x] Clicking "Logout" takes you to the login page
• [x] Log in with 'tester' / '1234', and then with the credentials from Section 1 succeeds
• [x] This time, DO NOT share "display name" or "country"
• [x] Clicking "Get Next Poem" loads different poem correctly x 3

SECTION 3: IMSHARER (http://localhost:5174/)

• [x] Main page loads
• [x] Upload of image works
• [x] Reload leads to instant reload (demonstrating proper caching)
• [x] Clicking the newly loaded image shows it in a lightbox