fix: add missing env variables (#325)

* fix: add missing env variables

* Added DATABASE_DIRECT_URL to README

* Updated text

* Added to build-time variable and removed default

* Removed extra connection string

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Co-authored-by: Keith Williams <keithwillcode@gmail.com>

.env.example

@@ -32,6 +32,9 @@ POSTGRES_PASSWORD=magical_password
 POSTGRES_DB=calendso
 DATABASE_HOST=database:5432
 DATABASE_URL=postgresql://${POSTGRES_USER}:${POSTGRES_PASSWORD}@${DATABASE_HOST}/${POSTGRES_DB}
+# Needed to run migrations while using a connection pooler like PgBouncer
+# Use the same one as DATABASE_URL if you're not using a connection pooler
+DATABASE_DIRECT_URL=${DATABASE_URL}
 GOOGLE_API_CREDENTIALS={}
 
 # Set this to '1' if you don't want Cal to collect anonymous usage