✨ Add Clear Cache button

Netbox Version	Plugin Version
v3.6.9	v0.25.1

Desired Behavior

In the "Cache Configuration" view of a Mapping entity, there should be a button labelled "Clear Cache".

Clicking that button should set a new field operation on the mapping to clear-cache so that we, as RPS squad, can configure a Webhook in Netbox to perform said operation.

For example:

sequenceDiagram
    actor SecOps
    participant Netbox
    participant AWX
    participant Job as AWX Job: clear_mapping_cache
    participant RPS_VM as RPS Virtual Machine

    SecOps-->>Netbox: Click "Purge Cache" button
    Netbox-->>Netbox: Set mapping "operation" field to "clear-cache"
    Netbox-->>AWX: Trigger Update Webhook on mapping
    AWX-->>Job: Trigger Job "clear_mapping_cache"
    Job-->>Netbox: Update mapping journal "operation clear-cache: pending"
    Job-->>RPS_VM: cURL with correct headers
    Job-->>Netbox: Update mapping journal "operation clear-cache: done (or failed)"
    Job-->>Netbox: Set mapping "operation" field to "none"

The new field operation is identical to how the Netbox Docker plugin works, see their source code:

• ChoiceSet
• Field in Container model
• Edit form
• Edit view controller
• URL entry in router
• Button in template

At the moment, the field operation should have the following available choices:

• clear-cache
• none

More could come later on.