fix multiple-user check, add tests, use local resolver for did:ethr

.env.sample

@@ -1,3 +1,4 @@
+# shellcheck disable=SC2034
 
 # These settings work for American Cloud.
 #S3_ACCESS_KEY=???
@@ -19,8 +20,6 @@ S3_SET_ACL=false
 #ENDORSER_API_URL=https://test-api.endorser.ch
 #ENDORSER_API_URL=https://api.endorser.ch
 
-INFURA_PROJECT_ID=???
-
 # host where the final image can be accessed by the public
 # default is https://test-image.timesafari.app
 #DOWNLOAD_IMAGE_SERVER=test-image.timesafari.app