validate endpoint can be a GET request

[pbashyal-nmdp]

Currently the validate endpoint is a POST request

curl -X 'POST' \
  'https://pyard-service.org/validate' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json' \
  -d '{
  "gl_string": "B*57:79N"
}'

It only has the gl_string payload, so can be a GET request

curl https://pyard-service.org/validate