Make more config items fully parametrizable

Allow a few more elements in lambda_config.template to be parametrized
by environment variables.

In the case of the DynamoDB table names, it's
better if the full name can be parametrized because not everything
necessarily matches the $PROJECT-cdn-$ENV_TYPE pattern (example: the
tables deployed by exodus-gw dev env don't).

In the case of the log format, it's useful to be able to switch the
format so that %(aws_request_id)s is avoided, as that variable won't be
available if the code runs outside the context of Lambda@Edge.

The default values of everything remains the same, except that an
unnecessary "\n" was removed from the end of the log format.

configuration/lambda_config.template

@@ -1,12 +1,12 @@
 {
   "table": {
-    "name": "$PROJECT-cdn-$ENV_TYPE",
+    "name": "$EXODUS_TABLE",
     "available_regions": [
       "us-east-1"
     ]
   },
   "config_table": {
-    "name": "$PROJECT-config-$ENV_TYPE",
+    "name": "$EXODUS_CONFIG_TABLE",
     "available_regions": [
       "us-east-1"
     ]
@@ -24,7 +24,7 @@
     "disable_existing_loggers": "False",
     "formatters": {
       "default": {
-        "format": "%(asctime)s - %(levelname)s - %(aws_request_id)s - %(message)s\n",
+        "format": "$EXODUS_LOG_FORMAT",
         "datefmt": "%Y-%m-%d %H:%M:%S"
       }
     },

scripts/mk-config

@@ -3,11 +3,14 @@ set -e
 
 export ORIGIN_RESPONSE_LOGGER_LEVEL=${ORIGIN_RESPONSE_LOGGER_LEVEL:-WARNING}
 export ORIGIN_REQUEST_LOGGER_LEVEL=${ORIGIN_REQUEST_LOGGER_LEVEL:-WARNING}
+export EXODUS_LOG_FORMAT="${EXODUS_LOG_FORMAT:-%(asctime)s - %(levelname)s - %(aws_request_id)s - %(message)s}"
 export EXODUS_HEADERS_MAX_AGE=${EXODUS_HEADERS_MAX_AGE:-600}
 export EXODUS_CONFIG_CACHE_TTL=${EXODUS_CONFIG_CACHE_TTL:-2}
 export EXODUS_COOKIE_TTL=${EXODUS_COOKIE_TTL:-720}
 export PROJECT=${PROJECT:-exodus}
 export ENV_TYPE=${ENV_TYPE:-dev}
+export EXODUS_TABLE=${EXODUS_TABLE:-$PROJECT-cdn-$ENV_TYPE}
+export EXODUS_CONFIG_TABLE=${EXODUS_CONFIG_TABLE:-$PROJECT-config-$ENV_TYPE}
 export EXODUS_SECRET_ARN=${EXODUS_SECRET_ARN}
 export EXODUS_KEY_ID=${EXODUS_KEY_ID}