# Domain Entities — U1 Hosting & Serving

**Note**: U1 introduces **no persisted entity**. It adds no table, no migration and no database column. Its "domain" consists of in-memory configuration descriptors and a response model. They are documented here because they are the data structures the unit's logic operates on, and because reviewers should be able to confirm that nothing is being persisted.

---

## Concept Relationships

```mermaid
graph TD
    host["Host application"]
    mountweb["StaticMount: website<br/>request path /"]
    mountadmin["StaticMount: admin SPA<br/>request path /admin"]
    provider["File provider<br/>per mount"]
    fallbackweb["SPA fallback: website"]
    fallbackadmin["SPA fallback: admin"]
    placeholder["Placeholder page<br/>embedded resource"]
    report["HealthReport<br/>response model"]
    orchestrator["ModuleOrchestrator<br/>existing"]
    bypass["Bypass prefix list<br/>existing, extended"]
    tokenparams["Token validation parameters<br/>existing, now shared"]

    host -->|"registers"| mountweb
    host -->|"registers"| mountadmin
    mountweb -->|"resolves files via"| provider
    mountadmin -->|"resolves files via"| provider
    mountweb -->|"falls back to"| fallbackweb
    mountadmin -->|"falls back to"| fallbackadmin
    fallbackweb -->|"substitutes when index absent"| placeholder
    host -->|"exposes"| report
    report -->|"reads module names from"| orchestrator
    host -->|"configures"| bypass
    host -->|"shares"| tokenparams
    bypass -->|"used by availability gate"| tokenparams

    classDef hostnode fill:#90cdf4,stroke:#2b6cb0,stroke-width:1px,color:#000;
    classDef mount fill:#9ae6b4,stroke:#2f855a,stroke-width:1px,color:#000;
    classDef model fill:#fbd38d,stroke:#c05621,stroke-width:1px,color:#000;
    classDef existing fill:#e2e8f0,stroke:#4a5568,stroke-width:1px,color:#000;
    class host hostnode;
    class mountweb,mountadmin,provider,fallbackweb,fallbackadmin,placeholder mount;
    class report model;
    class orchestrator,bypass,tokenparams existing;
```

Text alternative: the host registers two independent static mounts each with its own file provider and SPA fallback, plus a health response model that reads module names from the existing orchestrator; the bypass list and token validation parameters are existing structures this unit extends and shares.

---

## Static Mount Descriptor (configuration, in-memory)

Not a class to be persisted — this describes what each `UseStaticFiles` registration is configured with.

| Field | Website mount | Admin mount |
|---|---|---|
| Physical root | `{contentRoot}/wwwroot/web` | `{contentRoot}/wwwroot/admin` |
| Request path | `""` (root) | `/admin` |
| Default file | `index.html` | `index.html` |
| Directory browsing | Disabled | Disabled |
| Tolerates missing root | **Yes** — logs a warning | Yes — logs a warning |
| Registration order | Second | **First** |

**Registration order matters**: the admin mount must be registered first, or `/admin/...` would be resolved against the website root.

---

## HealthReport (response model, not persisted)

| Field | Type | Purpose |
|---|---|---|
| `status` | string | `"Healthy"`. A running process always reports healthy; absence of a response is the unhealthy signal |
| `timestamp` | timestamp with offset | When the report was produced, so a cached response is recognisable |
| `version` | string | The application's informational version, so a deploy can be confirmed without host access |
| `modules` | string array | Names of modules loaded by `ModuleOrchestrator` |

**Validation and constraints**:
- Every field is derived from in-process state. No field may require a database query, file read or network call (BR-U1-15).
- No field may contain configuration values, paths, connection details or environment variable contents (BR-U1-18).
- `modules` is read from the existing `ModuleOrchestrator.ModuleNames`, which is already exposed anonymously by `/api/v1/System/capabilities` — so this field introduces no new disclosure.

---

## Placeholder Page (embedded static content)

| Property | Value |
|---|---|
| Storage | Embedded resource in the assembly, not a file in `wwwroot` |
| Served when | The website fallback is needed and `wwwroot/web/index.html` is absent |
| Status code | `200` |
| Content | A statement that no website has been deployed yet, the expected target path, and a link to `/admin` |

**Why embedded rather than a file**: a file in `wwwroot/web/` would be inside the directory a website workspace owns and overwrites — it would be deleted by the first real website deployment, or worse, mistaken for part of the customer's site. Embedding keeps it outside that boundary entirely.

**What it must not contain**: no version, no environment name, no module list, no configuration. It is served anonymously to any visitor of the site root, which is a wider audience than `/health`.

---

## Extended Existing Structures

### Bypass prefix list (`AvailabilityMiddleware`)

| Aspect | Detail |
|---|---|
| Current contents | `/api/v1/Availability/status`, `/api/v1/Auth/`, `/api/v1/Setup/status`, `/api/v1/master/`, `/api/v1/SlaveStatus` |
| Added by U1 | `/health` |
| Matching | Case-insensitive prefix match, unchanged |

### Shared token validation parameters

| Aspect | Detail |
|---|---|
| Currently | Configured once inside `AddJwtBearer` in `ServiceCollectionExtensions.AddCoreInfrastructure` |
| Change | Extracted so the same instance is used by both the bearer scheme and the availability gate |
| Constraint | Exactly one definition. Two copies could drift, and a gate more permissive than the scheme would silently re-open the hole FR-24 closes |

---

## Persistence Summary

| Question | Answer |
|---|---|
| New tables? | None |
| New migrations? | None |
| New columns? | None |
| New configuration sections? | None — U1 adds no `appsettings` section |
| Anything written to disk at runtime? | No |

All persistence work in Round 1 belongs to **U2**, which adds the Data Protection keys table and the automatic Core migration.