add basic suppport for client_credentials oauth grant

Foxchat.Identity/Controllers/Oauth/AppsController.cs

@@ -0,0 +1,45 @@
+using Foxchat.Core;
+using Foxchat.Core.Models.Http;
+using Foxchat.Identity.Authorization;
+using Foxchat.Identity.Database;
+using Foxchat.Identity.Database.Models;
+using Microsoft.AspNetCore.Mvc;
+
+namespace Foxchat.Identity.Controllers.Oauth;
+
+[ApiController]
+[Authenticate]
+[Route("/_fox/ident/oauth/apps")]
+public class AppsController(ILogger logger, IdentityContext db) : ControllerBase
+{
+    [HttpPost]
+    public async Task<IActionResult> CreateApplication([FromBody] Apps.CreateRequest req)
+    {
+        var app = Application.Create(req.Name, req.Scopes, req.RedirectUris);
+        await db.AddAsync(app);
+        await db.SaveChangesAsync();
+
+        logger.Information("Created new application {Name} with ID {Id} and client ID {ClientId}", app.Name, app.Id, app.ClientId);
+
+        return Ok(new Apps.CreateResponse(
+            app.Id, app.ClientId, app.ClientSecret, app.Name, app.Scopes, app.RedirectUris
+        ));
+    }
+
+    [HttpGet]
+    public IActionResult GetSelfApp([FromQuery(Name = "with_secret")] bool withSecret)
+    {
+        var token = HttpContext.GetToken();
+        if (token is not { Account: null }) throw new ApiError.Forbidden("This endpoint requires a client token.");
+        var app = token.Application;
+
+        return Ok(new Apps.GetSelfResponse(
+            app.Id,
+            app.ClientId,
+            withSecret ? app.ClientSecret : null,
+            app.Name,
+            app.Scopes,
+            app.RedirectUris
+        ));
+    }
+}