API client generation

use generate.sh for client generation.

terraform provider generation

~/go/bin/tfplugingen-openapi generate --config dtz-rss2email-tf-config.yaml --output dtz-rss2email-provider-code-spec.json dtz-rss2email-api.yaml

~/go/bin/tfplugingen-framework generate all \
    --input dtz-rss2email-provider-code-spec.json \
    --output internal/provider