The URL to request the schema representation is the unique identifier.
We can't default to $request->getURL() since that's different for form submissions.
The schema.schema_url key is redundant, since the identifier is already contained on the top level 'id' key.
Keeping schema_url in a schema itself makes it less portable, particularly once we transition into
generic schemas which are not reliant on a particular record context (that's only contained in the schema_url)
This also fixes the issue of form schemas not refreshing after submit,
e.g. when form fields are added or removed.
Introducing <Tabs> component based on react-bootstrap
Better support for nested fields in FormBuilder
Tweaks to get FormBuilder working with frameworktest BasicFieldsPage fields
Added exception in FormBuilder when Component is defined but not found
Added check in SingleSelectField for empty value before adding one in
Added temporary workaround for CompositeFields with no name (another story to address the actual problem)
Added asset_preview_height for File image preview, matches the defined CSS max-height
Added documentation to DBFile::PreviewLink() method
