Retrieving the DTO happens as part of the metadata parsing, not recall. This way, we don't show the option to recall a nonexistent image.
This matches the flow for other metadata entities like models - we don't show the model recall button if the model isn't available.
In order to allow for null and undefined metadata values, this hook returned a symbol to indicate that parsing failed or was pending.
For values where the parsed value will never be null or undefined, it is useful get the value or null (instead of a symbol).
Model metadata includes the main model, VAE and refiner model.
These used full model configs, as returned by the server, as their metadata type.
LoRA and control adapter metadata only use the metadata identifier.
This created a difference in handling. After parsing a model/vae/refiner, we have its name and can display it. But for LoRAs and control adapters, we only have the model key and must query for the full model config to get the name.
This change makes main model/vae/refiner metadata only have the model key, like LoRAs and control adapters.
The render function is now async so fetching can occur within it. All metadata fields with models now only contain the identifier, and fetch the model name to render their values.
Add concepts for metadata handlers. Handlers include parsers, recallers and validators for different metadata types:
- Parsers parse a raw metadata object of any shape to a structured object.
- Recallers load the parsed metadata into state. Recallers are optional, as some metadata types don't need to be loaded into state.
- Validators provide an additional layer of validation before recalling the metadata. This is needed because a metadata object may be valid, but not able to be recalled due to some other requirement, like base model compatibility. Validators are optional.
Sometimes metadata is not a single object but a list of items - like LoRAs. Metadata handlers may implement an optional set of "item" handlers which operate on individual items in the list.
Parsers and validators are async to allow fetching additional data, like a model config. Recallers are synchronous.
The these handlers are composed into a public API, exported as a `handlers` object. Besides the handlers functions, a metadata handler set includes:
- A function to get the label of the metadata type.
- An optional function to render the value of the metadata type.
- An optional function to render the _item_ value of the metadata type.
