Convert ENV to JSON, filtered by prefix "WEB_APP_", with prefix removed, and with Boolean and Number values recognized. `jq` was used.

env to json, filtered by prefix, with type transformations

jq -n \
  'env
  | to_entries
  | map(select(.key | startswith("WEB_APP_")))
  | map({
    "key": (.key | sub("WEB_APP_"; "")),
    "value": (
      if (.value | test("^true$"; "i"))  then true
      elif (.value | test("^false$"; "i")) then false
      elif (.value | test("[[:digit:]]+")) then (.value | tonumber)
      elif (.value | test("^null$"; "i")) then null
      else .value end)})
 | from_entries'

E.g., the following ENV:

WEB_APP_STR="hello world"
WEB_APP_BOOL1="true"
WEB_APP_BOOL2="False"
WEB_APP_NUM="12345"
WEB_APP_NULL="null"

should return JSON:

{
  "STR": "hello world",
  "BOOL1": true,
  "BOOL2": false,
  "NUM": 12345,
  "NULL": null
}

Objects are not parsed, because DON'T PLACE OBJECTS INTO ENV!!!