connection.ConnectionOptions: fix a lot of issues

Various copypasta and typing errors around the thunks, some other
copypasta errors, etc. Also add a test which hits a decent chunk of
the API surface of ConnectionOptions, which is how these issues were
caught in the first place. This is an ugly test, but it has clearly
served its purpose.

tests/connection.zig

@@ -42,3 +42,105 @@ test "nats.Connection.connectTo" {
         defer connection.destroy();
     }
 }
+
+fn tokenHandler(userdata: *u32) [:0]const u8 {
+    _ = userdata;
+    return "token";
+}
+
+fn reconnectDelayHandler(userdata: *u32, connection: *nats.Connection, attempts: c_int) i64 {
+    _ = userdata;
+    _ = connection;
+    _ = attempts;
+
+    return 0;
+}
+
+fn errorHandler(
+    userdata: *u32,
+    connection: *nats.Connection,
+    subscription: *nats.Subscription,
+    status: nats.Status,
+) void {
+    _ = userdata;
+    _ = connection;
+    _ = subscription;
+    _ = status;
+}
+
+fn connectionHandler(userdata: *u32, connection: *nats.Connection) void {
+    _ = userdata;
+    _ = connection;
+}
+
+fn jwtHandler(userdata: *u32) nats.JwtResponseOrError {
+    _ = userdata;
+    // return .{ .jwt = std.heap.raw_c_allocator.dupeZ(u8, "abcdef") catch @panic("no!") };
+    return .{ .error_message = std.heap.raw_c_allocator.dupeZ(u8, "dang") catch @panic("no!") };
+}
+
+fn signatureHandler(userdata: *u32, nonce: [:0]const u8) nats.SignatureResponseOrError {
+    _ = userdata;
+    _ = nonce;
+    // return .{ .signature = std.heap.raw_c_allocator.dupe(u8, "01230123") catch @panic("no!") };
+    return .{ .error_message = std.heap.raw_c_allocator.dupeZ(u8, "whoops") catch @panic("no!") };
+}
+
+test "nats.ConnectionOptions" {
+    try nats.init(nats.default_spin_count);
+    defer nats.deinit();
+
+    const options = try nats.ConnectionOptions.create();
+    defer options.destroy();
+
+    var userdata: u32 = 0;
+
+    try options.setUrl(nats.default_server_url);
+    const servers = [_][*:0]const u8{ "nats://127.0.0.1:4442", "nats://127.0.0.1:4443" };
+    try options.setServers(&servers);
+    try options.setCredentials("user", "password");
+    try options.setToken("test_token");
+    // requires a functioning token handler, which I will not write right now. Also
+    // cannot be called if a token has already been set
+    // try options.setTokenHandler(u32, tokenHandler, &userdata);
+    try options.setNoRandomize(false);
+    try options.setTimeout(1000);
+    try options.setName("name");
+
+    // the following all require a build with openssl
+    // try options.setSecure(false);
+    // try options.setCiphers("-ALL:HIGH");
+    // try options.setCipherSuites("TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256");
+    // try options.setExpectedHostname("host.name");
+    // try options.skipServerVerification(true);
+    try options.setVerbose(true);
+    try options.setPedantic(true);
+    try options.setPingInterval(1000);
+    try options.setMaxPingsOut(100);
+    try options.setIoBufSize(1024);
+    try options.setAllowReconnect(false);
+    try options.setMaxReconnect(10);
+    try options.setReconnectWait(500);
+    try options.setReconnectJitter(100, 200);
+    try options.setCustomReconnectDelay(u32, reconnectDelayHandler, &userdata);
+    try options.setReconnectBufSize(1024);
+    try options.setMaxPendingMessages(50);
+    try options.setErrorHandler(u32, errorHandler, &userdata);
+    try options.setClosedCallback(u32, connectionHandler, &userdata);
+    try options.setDisconnectedCallback(u32, connectionHandler, &userdata);
+    try options.setDiscoveredServersCallback(u32, connectionHandler, &userdata);
+    try options.setLameDuckModeCallback(u32, connectionHandler, &userdata);
+    try options.ignoreDiscoveredServers(true);
+    try options.useGlobalMessageDelivery(false);
+    try options.ipResolutionOrder(.ipv4_first);
+    try options.setSendAsap(true);
+    try options.useOldRequestStyle(false);
+    try options.setFailRequestsOnDisconnect(true);
+    try options.setNoEcho(true);
+    try options.setRetryOnFailedConnect(u32, connectionHandler, true, &userdata);
+    try options.setUserCredentialsCallbacks(u32, u32, jwtHandler, signatureHandler, &userdata, &userdata);
+    try options.setWriteDeadline(5);
+    try options.disableNoResponders(true);
+    try options.setCustomInboxPrefix("_FOOBOX");
+    try options.setMessageBufferPadding(123);
+}