Add getEnvVar.ts to convert env vars to appropriate type (or undefined)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mifi/services-common",
-  "version": "1.0.6",
+  "version": "1.0.9",
   "author": "mifi (Mike Fitzpatrick)",
   "license": "MIT",
   "scripts": {
@@ -19,6 +19,7 @@
     "@babel/preset-typescript": "^7.21.5",
     "@tsconfig/node16": "^1.0.4",
     "@types/jest": "^29.5.1",
+    "@types/koa": "^2.13.6",
     "@types/node": "^20.2.3",
     "@typescript-eslint/eslint-plugin": "^5.59.2",
     "@typescript-eslint/parser": "^5.59.2",
@@ -31,6 +32,7 @@
     "eslint-plugin-prettier": "^4.2.1",
     "eslint-plugin-promise": "^6.0.0",
     "jest": "^29.5.0",
+    "koa": "^2.14.2",
     "prettier": "^2.8.4",
     "prettier-eslint": "^15.0.1",
     "prettier-eslint-cli": "^7.1.0",