[Player] Prefers Google Cloud for text-to-speech

Uses OpenAI as a fallback, but Google Cloud has a free tier
* Adds GOOGLE_APPLICATION_CREDENTIALS environment variable
* Adds documentation for Google application service account credentials

References #70

.env.example

@@ -10,6 +10,8 @@ DISCORD_BOT_CLIENT_ID=...
 DISCORD_BOT_CLIENT_SECRET=...
 DISCORD_BOT_TOKEN=...
 
+GOOGLE_APPLICATION_CREDENTIALS=./.data/google-application-service-account.json
+
 YOUTUBE_API_KEY=...
 YOUTUBE_COOKIES="..."
 SPOTIFY_CLIENT_ID=...

README.md

@@ -43,6 +43,8 @@ DISCORD_BOT_CLIENT_ID=...
 DISCORD_BOT_CLIENT_SECRET=...
 DISCORD_BOT_TOKEN=...
 
+GOOGLE_APPLICATION_CREDENTIALS=./.data/google-application-service-account.json
+
 YOUTUBE_API_KEY=...
 YOUTUBE_COOKIES="..."
 
@@ -80,6 +82,12 @@ UI_ROOT=http://localhost:8080
 
 If you are creating these environment variables for a cloud VM, make sure to change `ENVIRONMENT` to `production`, and replace `DATABASE_URL` with your production database URL (either the one from Heroku, or another service that you have set up).
 
+If you are using text-to-speech or otherwise using Google Applications, create a service account and place the JSON file here:
+
+```
+.data/google-application-service-account.json
+```
+
 ## Player Cookies
 
 Cookies are messy. Right now, there are three possible libraries used for the player (each can fail, so there are fallbacks):

deploy/docker-compose.yml

@@ -14,6 +14,7 @@ services:
       DISCORD_BOT_CLIENT_SECRET: ${DISCORD_BOT_CLIENT_SECRET}
       DISCORD_BOT_TOKEN: ${DISCORD_BOT_TOKEN}
       DATABASE_URL: ${DATABASE_URL}
+      GOOGLE_APPLICATION_CREDENTIALS: ${GOOGLE_APPLICATION_CREDENTIALS}
       YOUTUBE_API_KEY: ${YOUTUBE_API_KEY}
       YOUTUBE_COOKIES: ${YOUTUBE_COOKIES}
       SPOTIFY_CLIENT_ID: ${SPOTIFY_CLIENT_ID}

docs/DO-Instructions.md

@@ -50,6 +50,11 @@ These instructions describe a process for manually hosting the bot on a Digital
 
     You can use something like nano instead of vim if you struggle with the instructions above.
 
+1. (Optional) If you are using text-to-speech or otherwise using Google Applications, create a service account and place the JSON file here:
+
+    ```
+    .data/google-application-service-account.json
+    ```
 1. (Optional) If you want to expose your app to the outside world over HTTPS and a custom domain, then generate an SSL certificate and run the nginx server:
    1. Create a DNS A Record for your domain, and point it to the public IP address of your Digital Ocean Droplet.
    1. `npm run dhparam`