fixed env load for db creds in api backend

[anistark]

Fixed dotenv loading for DB and other config

DB config was not getting picked from env file. Added dotenv to load in for backend api.

Testing done

Connects successfully to db on build

[ervcz]

Hello @anistark, as a new dependency was added, and the pipeline fails the diff check after the go mod tidy command, I think the tidied up version should be committed to pass the diff check.

[ervcz]

Tests are failing as connections cannot be formed:

...
             	Test:       	TestGetApp/success
    --- FAIL: TestGetApp/success_product_id (0.17s)
        app_test.go:173: 
            	Error Trace:	/home/runner/work/nebraska/nebraska/backend/test/api/helper_test.go:104
            	            				/home/runner/work/nebraska/nebraska/backend/test/api/app_test.go:173
            	Error:      	Received unexpected error:
            	            	Get "http://localhost:8002/api/apps/io.kinvolk.sample": dial tcp [::1]:8002: connect: connection refused
            	Test:       	TestGetApp/success_product_id
--- FAIL: TestUpdateApp (0.34s)
    --- FAIL: TestUpdateApp/success (0.17s)
        app_test.go:200: 
            	Error Trace:	/home/runner/work/nebraska/nebraska/backend/test/api/helper_test.go:104
            	            				/home/runner/work/nebraska/nebraska/backend/test/api/app_test.go:200
            	Error:      	Received unexpected error:
            	            	Put "http://localhost:8002/api/apps/b6458005-8f40-4627-b33b-be70a718c48e": dial tcp [::1]:8002: connect: connection refused
...

[anistark]

Since there's too many changes to the project in the due time, it's getting difficult to rebase properly. Will reopen in a fresh PR.