chore: updating env var processing for CORS

Testing steps!

activate pyenv for unstructured-api (not -tools) and cd to root dir of unstructured-api-tools to run pip install -e . to install the current branch. (should see version.py ( 0.10.5 ) from this branch match output from pip list)
in the unstructured-api dir, run make generate-api
export ALLOWED_ORIGINS="http://example.com/,http://amanda.com" (important that the env var is a comma separated str) and start the app locally with make run-web-app
run curl and POST and OPTION requests to show the Access-Control-Allow-Origin header being set

example curl request: should see 200:

curl -X OPTIONS -H "Origin: http://example.com" -H "Access-Control-Request-Method: POST" -i http://localhost:8000/general/v0/general

curl -X OPTIONS -H "Origin: http://amanda.com" -H "Access-Control-Request-Method: POST" -i http://localhost:8000/general/v0/general

should see 400 (bad cors origin)

curl -X OPTIONS -H "Origin: http://localhost:3000" -H "Access-Control-Request-Method: POST" -i http://localhost:8000/general/v0/general

Unstructured-IO / unstructured-api-tools

chore: updating env var processing for CORS #174