Add channel test providers for Email, Slack, Teams, and Webhook

- Implemented EmailChannelTestProvider to generate email preview payloads.
- Implemented SlackChannelTestProvider to create Slack message previews.
- Implemented TeamsChannelTestProvider for generating Teams Adaptive Card previews.
- Implemented WebhookChannelTestProvider to create webhook payloads.
- Added INotifyChannelTestProvider interface for channel-specific preview generation.
- Created ChannelTestPreviewContracts for request and response models.
- Developed NotifyChannelTestService to handle test send requests and generate previews.
- Added rate limit policies for test sends and delivery history.
- Implemented unit tests for service registration and binding.
- Updated project files to include necessary dependencies and configurations.

docs/10_CONCELIER_CLI_QUICKSTART.md

@@ -12,7 +12,7 @@ runtime wiring, CLI usage) and leaves connector/internal customization for later
 - .NET SDK **10.0.100-preview** (matches `global.json`)
 - MongoDB instance reachable from the host (local Docker or managed)
 - `trivy-db` binary on `PATH` for Trivy exports (and `oras` if publishing to OCI)
-- Plugin assemblies present in `PluginBinaries/` (already included in the repo)
+- Plugin assemblies present in `StellaOps.Concelier.PluginBinaries/` (already included in the repo)
 - Optional: Docker/Podman runtime if you plan to run scanners locally
 
 > **Tip** – air-gapped installs should preload `trivy-db` and `oras` binaries into the
@@ -31,7 +31,7 @@ runtime wiring, CLI usage) and leaves connector/internal customization for later
    ```
 
 2. Edit `etc/concelier.yaml` and update the MongoDB DSN (and optional database name).
-   The default template configures plug-in discovery to look in `PluginBinaries/`
+   The default template configures plug-in discovery to look in `StellaOps.Concelier.PluginBinaries/`
    and disables remote telemetry exporters by default.
 
 3. (Optional) Override settings via environment variables. All keys are prefixed with
@@ -71,7 +71,7 @@ runtime wiring, CLI usage) and leaves connector/internal customization for later
    environment. Authority expects per-plugin manifests in `etc/authority.plugins/`;
    sample `standard.yaml` and `ldap.yaml` files are provided as starting points.
    For air-gapped installs keep the default plug-in binary directory
-   (`../PluginBinaries/Authority`) so packaged plug-ins load without outbound access.
+   (`../StellaOps.Authority.PluginBinaries`) so packaged plug-ins load without outbound access.
 
 3. Environment variables prefixed with `STELLAOPS_AUTHORITY_` override individual
    fields. Example: