[Enh]: New auth provider `ApiKey`

## Header syntax

```http
GET /api/Book
X-API-Key: super-secret-value
X-MS-API-ROLE: api-client
```
## Configuration

```json
"authentication": {
"provider": "ApiKey",
"api-key": {
"header": "X-API-Key",
"keys": [
{
"name": "internal-service-a",
"key": "@env('DAB_SERVICE_A_API_KEY')",
"roles": [ "service-a" ]
},
{
"name": "internal-service-b",
"key": "@env('DAB_SERVICE_B_API_KEY')",
"roles": [ "service-b" ]
}
]
}
}
```

## Command line

```bash
dab configure --runtime.host.authentication.api-key.keys "internal-service-a:@env('DAB_SERVICE_A_API_KEY'):service-a"
dab configure --runtime.host.authentication.api-key.keys "internal-service-b:@env('DAB_SERVICE_B_API_KEY'):service-b"
```

Start by tracing the existing authentication configuration under runtime.host.authentication and the dab configure command; the issue names no files or tests. Done means the ApiKey provider supports the shown header, configuration, role header, and CLI key entries, with coverage for these examples.

Written by the indexing model from the issue text.