feat(transport): Language option (Accept-Language), DTOs from gateway refactoringV2 1c4e974f7

README.md

@@ -111,6 +111,7 @@ NORBIX_API_KEY=sk_live_...
 NORBIX_PROJECT_ID=proj_123
 NORBIX_ACCOUNT_ID=acc_456            # optional
 NORBIX_REGION=nb-eu-germany          # optional — no default region (see "Regions")
+NORBIX_LANGUAGE=lt                   # optional — sent as Accept-Language (see "Language")
 NORBIX_API_URL=https://api.norbix.ai
 NORBIX_HUB_URL=https://hub.norbix.ai
 NORBIX_API_VERSION=v3
@@ -235,6 +236,31 @@ await client.Account.UpdateProjectRegionsAsync(new UpdateProjectRegions
 
 Every other project setting (name, CORS, languages, admin URL, legal, Admin Portal, AI) is on [docs/hub/project.md](./docs/hub/project.md).
 
+## Language
+
+The gateway reads exactly one language input: the standard `Accept-Language` header (q-values are honoured; the project's default language is used when nothing matches). The response says which language it picked in `Content-Language`. The old `cultureCode` request field and the `CultureCode` / `norbix-language` headers are gone — the SDK never sends them.
+
+The SDK resolves the language like the region — there is **no default language**:
+
+1. Per-call override — `client.WithLanguage("...")`
+2. `Language` on `NorbixClientOptions` (explicit values win over env vars)
+3. `NORBIX_LANGUAGE` environment variable
+4. Unset — no `Accept-Language` header is sent and the gateway uses the project default
+
+The value is sent as-is, so a single tag or a full header value both work:
+
+```csharp
+var client = new NorbixApiClient(new NorbixClientOptions
+{
+    ProjectId = "proj_123",
+    ApiKey = "<api_key>",
+    Language = "lt-LT, en;q=0.8",
+});
+
+var lt = client.WithLanguage("lt");      // shares the HttpClient, like WithRegion
+var dflt = client.WithLanguage(null);    // clears it — header omitted, project default
+```
+
 ## Project vs Account Scope
 
 - `ProjectId` is required. The SDK works at project scope by default.

src/Norbix.Contracts/NorbixClientOptions.cs

@@ -59,6 +59,19 @@ public sealed class NorbixClientOptions
     /// </summary>
     public string? Region { get; set; }
 
+    /// <summary>
+    /// Preferred response language, sent as the standard <c>Accept-Language</c>
+    /// header — a single tag (e.g. <c>lt</c>, <c>lt-LT</c>) or a full header
+    /// value with q-values (e.g. <c>lt-LT, en;q=0.8</c>). The gateway honours
+    /// the q-values and falls back to the project's default language when
+    /// nothing matches; the chosen language comes back as
+    /// <c>Content-Language</c>. Like <see cref="Region"/> there is NO default —
+    /// when unset, no header is sent. Resolution order: per-call
+    /// <c>WithLanguage</c> override on the client → this option →
+    /// <c>NORBIX_LANGUAGE</c> environment variable → unset.
+    /// </summary>
+    public string? Language { get; set; }
+
     /// <summary>API gateway base URL. Default <c>https://api.norbix.ai</c> (or <c>NORBIX_API_URL</c>).</summary>
     public string ApiBaseUrl { get; set; } = DefaultApiBaseUrl;
 
@@ -102,6 +115,7 @@ public NorbixClientOptions Clone()
             AccountId = AccountId,
             Env = Env,
             Region = Region,
+            Language = Language,
             ApiBaseUrl = ApiBaseUrl,
             HubBaseUrl = HubBaseUrl,
             ApiVersion = ApiVersion,
@@ -142,6 +156,7 @@ source is null
         if (env is not null) Env = env;
 
         Region ??= NullIfEmpty(Read("NORBIX_REGION"));
+        Language ??= NullIfEmpty(Read("NORBIX_LANGUAGE"));
 
         var apiUrl = NullIfEmpty(Read("NORBIX_API_URL"));
         if (apiUrl is not null) ApiBaseUrl = apiUrl;