Refactor helper script to create a Capsule user (#454)

* chore(hack/create-user.sh): let pick bash interpreter from path

bash interpreter binary could be put at different paths than /bin/bash.

Signed-off-by: maxgio92 <massimiliano.giovagnoli.1992@gmail.com>

* refactor(hack/create-user.sh): add helper function to apply dry

add helper function to check commands existence.

Signed-off-by: maxgio92 <massimiliano.giovagnoli.1992@gmail.com>

hack/create-user.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 # This script uses Kubernetes CertificateSigningRequest (CSR) to generate a
 # certificate signed by the Kubernetes CA itself.
@@ -10,23 +10,18 @@
 # Exit immediately if a command exits with a non-zero status.
 set -e
 
-# Check if OpenSSL is installed
-if [[ ! -x "$(command -v openssl)" ]]; then
-    echo "Error: openssl not found"
-    exit 1
-fi
+function check_command() {
+    local command=$1
 
-# Check if kubectl is installed
-if [[ ! -x "$(command -v kubectl)" ]]; then
-    echo "Error: kubectl not found"
-    exit 1
-fi
+    if ! command -v $command &> /dev/null; then
+        echo "Error: ${command} not found"
+        exit 1
+    fi
+}
 
-# Check if jq is installed
-if [[ ! -x "$(command -v jq)" ]]; then
-    echo "Error: jq not found"
-    exit 1
-fi
+check_command openssl
+check_command kubectl
+check_command jq
 
 USER=$1
 TENANT=$2