fix(core): add credential and siwe to trustedProviders type

- Replace 'email-password' with 'credential' (the actual providerId used)
- Add 'siwe' for Sign-In with Ethereum plugin support
- Update documentation to use 'credential' instead of 'email-password'

The previous 'email-password' value in the type didn't match any actual
providerId - password-based accounts use 'credential' as their providerId.

Co-authored-by: taesu <taesu@better-auth.com>

docs/content/docs/guides/workos-migration-guide.mdx

@@ -115,7 +115,7 @@ export const auth = betterAuth({
   account: { // [!code highlight]
     accountLinking: { // [!code highlight]
       enabled: true, // [!code highlight]
-      trustedProviders: ["email-password", "github"], // [!code highlight]
+      trustedProviders: ["credential", "github"], // [!code highlight]
     }, // [!code highlight]
   }, // [!code highlight]
 });

docs/content/docs/reference/options.mdx

@@ -408,7 +408,7 @@ export const auth = betterAuth({
 		storeAccountCookie: true, // Store account data after OAuth flow in a cookie (useful for database-less flows)
 		accountLinking: {
 			enabled: true,
-			trustedProviders: ["google", "github", "email-password"],
+			trustedProviders: ["google", "github", "credential"],
 			allowDifferentEmails: false
 		}
 	},

packages/core/src/types/init-options.ts

@@ -927,7 +927,7 @@ export type BetterAuthOptions = {
 					 */
 					trustedProviders?: Array<
 						LiteralUnion<
-							SocialProviderList[number] | "email-password" | "sso",
+							SocialProviderList[number] | "credential" | "sso" | "siwe",
 							string
 						>
 					>;