add a bunch of stuff copied from Foxchat.NET

Foxnouns.Backend/Database/DatabaseQueryExtensions.cs

@@ -0,0 +1,47 @@
+using System.Security.Cryptography;
+using Foxnouns.Backend.Database.Models;
+using Foxnouns.Backend.Utils;
+using Microsoft.EntityFrameworkCore;
+
+namespace Foxnouns.Backend.Database;
+
+public static class DatabaseQueryExtensions
+{
+    public static async Task<User> ResolveUserAsync(this DatabaseContext context, string userRef)
+    {
+        User? user;
+        if (Snowflake.TryParse(userRef, out var snowflake))
+        {
+            user = await context.Users
+                .Include(u => u.Members)
+                .FirstOrDefaultAsync(u => u.Id == snowflake);
+            if (user != null) return user;
+        }
+
+        user = await context.Users
+            .Include(u => u.Members)
+            .FirstOrDefaultAsync(u => u.Username == userRef);
+        if (user != null) return user;
+        throw new FoxnounsError.UnknownEntityError(typeof(User));
+    }
+
+    public static async Task<Application> GetFrontendApplicationAsync(this DatabaseContext context)
+    {
+        var app = await context.Applications.FirstOrDefaultAsync(a => a.Id == new Snowflake(0));
+        if (app != null) return app;
+
+        app = new Application
+        {
+            Id = new Snowflake(0),
+            ClientId = RandomNumberGenerator.GetHexString(32, true),
+            ClientSecret = OauthUtils.RandomToken(48),
+            Name = "pronouns.cc",
+            Scopes = ["*"],
+            RedirectUris = [],
+        };
+
+        context.Add(app);
+        await context.SaveChangesAsync();
+        return app;
+    }
+}