feat: Allow configuring the OAuth compatibility mode

src/core/config/mod.rs

@@ -669,6 +669,10 @@ pub struct Config {
 	#[serde(default)]
 	pub registration_terms: HashMap<String, HashMap<String, TermsDocument>>,
 
+	/// display: nested
+	#[serde(default)]
+	pub oauth: OauthConfig,
+
 	/// Controls whether encrypted rooms and events are allowed.
 	#[serde(default = "true_fn")]
 	pub allow_encryption: bool,
@@ -2358,6 +2362,43 @@ pub struct TermsDocument {
 	pub url: String,
 }
 
+#[derive(Clone, Debug, Default, Deserialize)]
+#[config_example_generator(
+	filename = "conduwuit-example.toml",
+	section = "global.oauth",
+	optional = "true"
+)]
+pub struct OauthConfig {
+	/// The compatibility mode to use for OAuth.
+	///
+	/// - "disabled": OAuth will be unavailable. Users will only be able to log
+	///   in using legacy authentication.
+	/// - "hybrid": OAuth and legacy authentication will both be available. Some
+	///   clients may only use one or the other.
+	/// - "exclusive": Only OAuth will be available. Clients which require
+	///   legacy authentication will be unable to log in.
+	///
+	/// default: "hybrid"
+	pub compatibility_mode: OAuthMode,
+}
+
+#[derive(Clone, Debug, Default, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum OAuthMode {
+	Disabled,
+	#[default]
+	Hybrid,
+	Exclusive,
+}
+
+impl OAuthMode {
+	#[must_use]
+	pub fn uiaa_available(&self) -> bool { matches!(self, Self::Disabled | Self::Hybrid) }
+
+	#[must_use]
+	pub fn oauth_available(&self) -> bool { matches!(self, Self::Hybrid | Self::Exclusive) }
+}
+
 const DEPRECATED_KEYS: &[&str] = &[
 	"cache_capacity",
 	"conduit_cache_capacity_modifier",

src/core/error/response.rs

@@ -73,11 +73,8 @@ pub(super) fn bad_request_code(kind: &ErrorKind) -> StatusCode {
 		// 413
 		| TooLarge => StatusCode::PAYLOAD_TOO_LARGE,
 
-		// 405
-		| Unrecognized => StatusCode::METHOD_NOT_ALLOWED,
-
 		// 404
-		| NotFound => StatusCode::NOT_FOUND,
+		| Unrecognized | NotFound => StatusCode::NOT_FOUND,
 
 		// 403
 		| GuestAccessForbidden