[#446] Redis authentication support

Previously we did not support authentication for redis anywhere. Also in the docker compose we were exposing redis port 6379 without any authentication. In the app side for the connections that app server (for storing keys as well as for socket connections made using action cable) and Sidekiq were making to redis server did not support authentication.

With this commit, we support authentication for redis connections from app side and Sidekiq. This is supported in docker-compose as well.

The changes include :
* Added support for new env variable REDIS_PASSWORD
* This redis password is now supported by action cable connections, Sidekiq connections and app side redis connections
* Since Sidekiq did not have an initializer, added an initializer to pass custom config to Sidekiq (for now it's options for redis)
* Changes in docker-compose to pickup a password set in .env file to protect the redis server running in docker
* Added necessary documentation changes in `docker.md` and `environment-variables.md`

docs/development/environment-setup/docker.md

@@ -7,6 +7,13 @@ title: "Docker Setup and Debugging Guide"
 
 After cloning the repo and installing docker on your machine, run the following command from the root directory of the project.
 
+```bash
+cp .env.example .env
+```
+
+Make changes to the `.env` file as required [Optional]. If you want to set the password for redis when you run
+docker-compose, set any string value to the environment variable `REDIS_PASSWORD` in the `.env` file. which will secure the redis running inside docker-compose with this password. This will be automatically picked up by app server and sidekiq, to authenticate while making connections to redis server.
+
 ```bash
 docker-compose build
 ```

docs/development/project-setup/environment-variables.md

@@ -60,7 +60,7 @@ AWS_SECRET_ACCESS_KEY=
 AWS_REGION=
 ```
 
-### Configure Redis URL
+### Configure Redis
 
 For development, you can use the following url to connect to redis.
 
@@ -68,6 +68,13 @@ For development, you can use the following url to connect to redis.
 REDIS_URL='redis:://127.0.0.1:6379'
 ```
 
+To authenticate redis connections made by app server and sidekiq, if it's protected by a password, use the following
+environment variable to set the password.
+
+```bash
+REDIS_PASSWORD=
+```
+
 ### Configure Postgres host
 
 You can set the following environment variable to set the host for postgres.