You should create a new Apple ID, ideally one that’s not associated to a person. Generate an App-Specific password using that new account. Finally invite the new Apple ID into the business account’s Apple Developer Program as a Developer role. Alternatively you could also create an API Key file and use that one for authentication. Search the web for “How to Securely Provide Apple ID Password into Notarization Build Jobs” for more details on using a dedicated Apple ID for notarization or creating and using an API key for that purpose (obviously I can’t link it here due to forum restrictions).

You could have another copy of your app (and thus, extension) installed that is not built for debugging. The Photos app could have loaded that one instead of the one made by Xcode. In this case, you could temporarily move all other copies of your app to the Trash and re-launch Photos in Xcode to debug your app extension.

This remains true as per Xcode 15.1 The folder "~/Library/Developer" needs to be a real folder, not a symlink to somewhere else.

This is a desired behavior since Flash SMS has been abused to send marketing messages. Moreover, some telcos themselves are abusing these Flash SMS and use this method to send their own marketing messages.