fix: model register missing model-type and not accepting metadata (#11)

# What does this PR do?
Added the ability to specify the model type when registering models. 
Also fixed a bug with passing metadata which would result in the
following error:
```
Error Type: BadRequestError                                                                                                                                     │
│ Details: Error code: 400 - {'error': {'detail': {'errors': [{'loc': ['body', 'metadata'], 'msg': 'Input should be a valid dictionary', 'type': 'dict_type'}]}}}
```

Closes: #215
## Test Plan
Run the following commands
```
# Note a Llama Stack Server must be running
# Create a venv
uv sync --python 3.12
# Install the LSC with the new code changes
uv pip install -e .
# List the available models
llama-stack-client models list
# Register the granite-embedding-30m embedding model NOTE must have sentence-transformers as an inference provider
llama-stack-client models register granite-embedding-30m --provider-id "sentence-transformers" --provider-model-id ibm-granite/granite-embedding-30m-english --metadata '{"embedding_dimension": 384}' --model-type embedding
# Verify the embedding model added are present
llama-stack-client models list
```

Author: Bobbins228

src/llama_stack_client/lib/cli/models/models.py

@@ -4,6 +4,7 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import json
 from typing import Optional
 
 import click
@@ -93,12 +94,23 @@ def get_model(ctx, model_id: str):
     console.print(table)
 
 
+class JSONParamType(click.ParamType):
+    name = "json"
+
+    def convert(self, value, param, ctx):
+        try:
+            return json.loads(value)
+        except json.JSONDecodeError as e:
+            self.fail(f"Invalid JSON: {e}", param, ctx)
+
+
 @click.command(name="register", help="Register a new model at distribution endpoint")
 @click.help_option("-h", "--help")
 @click.argument("model_id")
 @click.option("--provider-id", help="Provider ID for the model", default=None)
 @click.option("--provider-model-id", help="Provider's model ID", default=None)
-@click.option("--metadata", help="JSON metadata for the model", default=None)
+@click.option("--metadata", type=JSONParamType(), help="JSON metadata for the model", default=None)
+@click.option("--model-type", type=click.Choice(["llm", "embedding"]), default="llm", help="Model type: llm, embedding")
 @click.pass_context
 @handle_client_errors("register model")
 def register_model(
@@ -107,6 +119,7 @@ def register_model(
     provider_id: Optional[str],
     provider_model_id: Optional[str],
     metadata: Optional[str],
+    model_type: Optional[str],
 ):
     """Register a new model at distribution endpoint"""
     client = ctx.obj["client"]
@@ -117,6 +130,7 @@ def register_model(
         provider_id=provider_id,
         provider_model_id=provider_model_id,
         metadata=metadata,
+        model_type=model_type,
     )
     if response:
         console.print(f"[green]Successfully registered model {model_id}[/green]")