Support setting multiple secrets at once

[pilosus]

For now workflow_secret supports setting just one key-value at once. Setting multiple secrets requires explicit looping over the keys:

$ cat key_val.txt
SECRET_KEY1=VALUE1
SECRET_KEY2=VALUE2
SECRET_KEY3=VALUE3

$ cat key_val.txt | while IFS='=' read key value; do
    workflow_secret --owner=anna-money --repo=workflow-tools \
      --token="YOUR-PERSONAL-ACCESS-TOKEN" \
      update --key=$key --value=$value
done
{"message": "Secret updated"}
{"message": "Secret updated"}
{"message": "Secret updated"}

It's awkward, it requires to much coding. Let's support bulk operations to create/update secrets.

Things to take into consideration:

• GitHub is rate limiting requests to the API (5000 reqs/hour)
• Given the rate limits no async requests really needed, let's do it simple first
• Stick to existing workflow_tools convention: we can read secret key-value pairs from envfile like we do in workflow_generator when invoked with option -e