docs: add description frontmatter to content pages for SEO (#11654)

apps/docs/content/apis/openidoauth/authn-methods.mdx

@@ -1,5 +1,6 @@
 ---
 title: Authentication Methods in ZITADEL
+description: "The supported client authentication methods in ZITADEL, including Client Secret and JWT."
 sidebar_label: Authentication Methods
 ---
 

apps/docs/content/apis/openidoauth/authrequest.mdx

@@ -1,5 +1,6 @@
 ---
 title: ZITADEL OIDC Authentication Request Playground
+description: "The OIDC playground for testing and constructing authentication requests."
 sidebar_label: OIDC Playground
 ---
 

apps/docs/content/apis/openidoauth/claims.mdx

@@ -1,5 +1,6 @@
 ---
 title: Claims in ZITADEL
+description: "Standard OIDC and custom claims issued by ZITADEL in ID tokens, access tokens, and via the Userinfo endpoint."
 sidebar_label: Claims
 ---
 

apps/docs/content/apis/openidoauth/endpoints.mdx

@@ -1,5 +1,6 @@
 ---
 title: OpenID Connect Endpoints in ZITADEL
+description: "The standard OIDC and OAuth 2.0 endpoints for ZITADEL, adhering to the OpenID Connect 1.0 standard."
 sidebar_label: OpenID Connect Endpoints
 ---
 

apps/docs/content/apis/openidoauth/grant-types.mdx

@@ -1,5 +1,6 @@
 ---
 title: Grant Types in ZITADEL
+description: "The OAuth 2.0 grant types supported by ZITADEL, such as Authorization Code and Client Credentials."
 sidebar_label: Grant Types
 ---
 

apps/docs/content/apis/openidoauth/scopes.mdx

@@ -1,5 +1,6 @@
 ---
 title: Scopes in ZITADEL
+description: "The standard and ZITADEL-specific OIDC scopes available for identity and authentication requests."
 sidebar_label: Scopes
 ---