Fix security issues (#244)

* fix security issues in react-rust-postgres sample
* fix security issues in react-java-mysql sample
* fix security issues in react-express-mysql sample
* fix security issues in react-express-mongodb sample
* fix security issues in react-nginx sample
* fix security issues in angular sample
* fix security issues in django sample
* fix security issues in vuejs sample

Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>