REST: Disallow unnecessary string interpolation

This disallows expressions like `${foo}`. The error message is a bit
unfortunate, but it does what we want it to do.

Change-Id: I5fc59e7b2f588c681253346e70e05e4a365f8a94

repo/rest-api/.eslintrc.json

@@ -13,6 +13,7 @@
 		"no-unused-expressions": "off",
 		"prefer-arrow-callback": "off",
 		"template-curly-spacing": "off",
-		"camelcase": "off"
+		"camelcase": "off",
+		"no-implicit-coercion": [ "error", { "disallowTemplateShorthand": true } ]
 	}
 }