Retrieves a URL generated by the Media Manager to use when creating a submission that includes a field for uploading files.
Note: You need at least a Standard Premium plan for your site to upload files.
To learn how external clients can use the generated upload URL to upload a file to the Media Manager, see Upload API.
Form ID.
Name of file to upload.
Mime type of file to upload.
For example, 'image/png'
This method doesn’t return any custom errors, but may return standard errors. Learn more about standard Wix errors.