[MOB-8225] Add env variable to turn off jwt requirement for sample app

[pauljung14]

JIRA Ticket(s) if any

• MOB-8225

Description

Branches off MOB-8047.
This was requested to resolve issues with testing AUT on Web SDK.
Can turn off JWT requirement (and consequently the need for VPN too) using an environment variable.

Test Steps

Set USE_JWT=false

1. Set USE_JWT=false in /react-example/.env
2. Use an API key configured to not require JWT
3. Load react sample app
4. Log in
5. Expected: Can log in successfully
6. Use an API key configured to require JWT
7. Expected: Cannot log in

Do not set USE_JWT=false

1. Do not set USE_JWT=false (comment it out)
2. Use an API key configured to not require JWT
3. Load react sample app
4. Log in
5. Expected: Cannot log in
6. Use a valid API key and JWT secret in your env file
7. Expected: Can log in successfully