fix: address appliance v8 install review findings

- install: resolve the image directory from the version's settings type and
  skip image handling for docker appliances; guard appliance.images
- appliance schema: validate template_properties against template_type,
  align cpu_throttling with the qemu template, add kvm and version idlepc
- conversion: map IOU image to path, kvm disable to accel=tcg, inherit only
  same-type default settings, symbol fallback from the effective category,
  template_properties cannot override structural fields
- allow clearing netmiko_device_type with an empty string
- download the template symbol regardless of the level it is defined at and
  give qemu guests a default symbol

gns3server/schemas/controller/appliances.py

@@ -19,7 +19,7 @@
 from enum import Enum
 from typing import Annotated, List, Literal, Optional, Union
 from uuid import UUID
-from pydantic import AnyUrl, BaseModel, Discriminator, EmailStr, Field, Tag
+from pydantic import AnyUrl, BaseModel, Discriminator, EmailStr, Field, Tag, model_validator
 from ..common import ExtraConfig
 
 
@@ -567,14 +567,23 @@ class QemuPropertiesV8(BaseModel):
         title='Optional define the disk boot priory. Refer to -boot option in qemu manual for more details.',
     )
     kernel_command_line: Optional[str] = Field(None, title='Command line parameters send to the kernel')
+    kvm: Optional[Kvm] = Field(None, title='KVM requirements')
     options: Optional[str] = Field(None, title='Optional additional qemu command line options')
-    cpu_throttling: Optional[Annotated[float, Field(ge=0.0, le=100.0)]] = Field(None, title='Throttle the CPU')
+    cpu_throttling: Optional[Annotated[int, Field(ge=0, le=800)]] = Field(None, title='Throttle the CPU')
     tpm: Optional[bool] = Field(None, title='Enable the Trusted Platform Module (TPM)')
     uefi: Optional[bool] = Field(None, title='Enable the UEFI boot mode')
     on_close: Optional[QemuOnClose] = Field(None, title='Action to execute on the VM is closed')
     process_priority: Optional[QemuProcessPriority] = Field(None, title='Process priority for QEMU')
 
 
+_V8_PROPERTIES_MODELS = {
+    TemplateType.qemu: QemuPropertiesV8,
+    TemplateType.dynamips: DynamipsPropertiesV8,
+    TemplateType.iou: IouPropertiesV8,
+    TemplateType.docker: DockerPropertiesV8,
+}
+
+
 class TemplateSetting(BaseModel):
     """Emulator settings configuration (v8)"""
 
@@ -587,12 +596,34 @@ class TemplateSetting(BaseModel):
         title='Properties for the template'
     )
 
+    @model_validator(mode='before')
+    @classmethod
+    def _validate_template_properties(cls, data):
+        """
+        Validate template_properties against the model matching template_type.
+        The template_type discriminator lives at the settings level (not inside
+        template_properties), so the union cannot be discriminated by pydantic
+        alone and would misroute properties between the per-type models.
+        """
+
+        if isinstance(data, dict):
+            # work on a copy: replacing template_properties with the validated
+            # model must not mutate the caller's data
+            data = data.copy()
+            template_type = data.get("template_type")
+            template_properties = data.get("template_properties")
+            model = _V8_PROPERTIES_MODELS.get(template_type)
+            if model is not None and isinstance(template_properties, dict):
+                data["template_properties"] = model.model_validate(template_properties)
+        return data
+
 
 class ApplianceVersionV8(BaseModel):
     """Appliance version definition (v8)"""
 
     name: str = Field(..., title='Name of the version')
     settings: Optional[str] = Field(None, title='Template settings to use to run the version')
+    idlepc: Optional[str] = Field(None, pattern=r'^0x[0-9a-f]{8}')
     category: Optional[Category] = Field(None, title='Category of the version')
     installation_instructions: Optional[str] = Field(None, title='Optional installation instructions for the version')
     usage: Optional[str] = Field(None, title='Optional instructions about using the version')
@@ -633,7 +664,7 @@ class ApplianceV1_6(BaseModel):
     usage: Optional[str] = Field(None, title='How to use the appliance')
     symbol: Optional[str] = Field(None, title='An optional symbol for the appliance')
     netmiko_device_type: Optional[str] = Field(
-        None, title='Device type for Netmiko-based automation tools', pattern=r'^[a-z0-9_]+$'
+        None, title='Device type for Netmiko-based automation tools', pattern=r'^[a-z0-9_]+$|^$'
     )
     first_port_name: Optional[str] = Field(None, title='Optional name of the first networking port example: eth0')
     port_name_format: Optional[str] = Field(None, title='Optional formating of the networking port example: eth{0}')
@@ -689,7 +720,7 @@ class ApplianceV8(BaseModel):
     default_password: Optional[str] = Field(None, title='Default password for the appliance')
     symbol: Optional[str] = Field(None, title='An optional symbol for the appliance')
     netmiko_device_type: Optional[str] = Field(
-        None, title='Device type for Netmiko-based automation tools', pattern=r'^[a-z0-9_]+$'
+        None, title='Device type for Netmiko-based automation tools', pattern=r'^[a-z0-9_]+$|^$'
     )
     tags: Optional[List[str]] = Field(None, title='User-defined metadata tags for the appliance')
     settings: List[TemplateSetting] = Field(..., title='Settings for running the appliance')

gns3server/schemas/controller/nodes.py

@@ -119,7 +119,7 @@ class NodeBase(BaseModel):
     netmiko_device_type: Optional[str] = Field(
         None,
         description="Device type for Netmiko-based automation tools, overrides the template value",
-        pattern=r"^[a-z0-9_]+$",
+        pattern=r"^[a-z0-9_]+$|^$",
     )
     aux: Optional[int] = Field(None, gt=0, le=65535, description="Auxiliary console TCP port")
     aux_type: Optional[ConsoleType] = None

gns3server/schemas/controller/templates/__init__.py

@@ -51,7 +51,7 @@ class TemplateBase(BaseModel):
     netmiko_device_type: Optional[str] = Field(
         None,
         description="Device type for Netmiko-based automation tools (e.g. 'cisco_xr' or 'nokia_srl')",
-        pattern=r"^[a-z0-9_]+$",
+        pattern=r"^[a-z0-9_]+$|^$",
     )
     tags: Optional[List[str]] = Field(
         default_factory=list,