doc: Add doc link to as_str implementations

crates/ruma-client-api/src/doc/string_enum.md

@@ -1,4 +1,5 @@
 <!-- Keep this comment so the content is always included as a new paragraph -->
 This type can hold an arbitrary string. To build this with a custom value, convert it from a
 string with `::from()` / `.into()`. To check for formats that are not available as a
-documented variant here, use its string representation, obtained through `.as_str()`.
+documented variant here, use its string representation, obtained through
+[`.as_str()`](Self::as_str()).

crates/ruma-common/src/doc/string_enum.md

@@ -1,4 +1,5 @@
 <!-- Keep this comment so the content is always included as a new paragraph -->
 This type can hold an arbitrary string. To build this with a custom value, convert it from a
 string with `::from()` / `.into()`. To check for formats that are not available as a
-documented variant here, use its string representation, obtained through `.as_str()`.
+documented variant here, use its string representation, obtained through
+[`.as_str()`](Self::as_str()).

crates/ruma-federation-api/src/query/get_profile_information.rs

@@ -82,7 +82,8 @@ pub mod v1 {
     ///
     /// This type can hold an arbitrary string. To build this with a custom value, convert it from a
     /// string with `::from() / .into()`. To check for formats that are not available as a
-    /// documented variant here, use its string representation, obtained through `.as_str()`.
+    /// documented variant here, use its string representation, obtained through
+    /// [`.as_str()`](Self::as_str()).
     #[derive(Clone, Debug, PartialEq, Eq, StringEnum)]
     #[non_exhaustive]
     pub enum ProfileField {

crates/ruma-identity-service-api/src/lookup.rs

@@ -12,7 +12,7 @@ pub mod lookup_3pid;
 ///
 /// This type can hold an arbitrary string. To build this with a custom value, convert it from a
 /// string with `::from() / .into()`. To check for formats that are not available as a documented
-/// variant here, use its string representation, obtained through `.as_str()`.
+/// variant here, use its string representation, obtained through [`.as_str()`](Self::as_str()).
 #[derive(Debug, PartialEq, Eq, Clone, StringEnum)]
 #[non_exhaustive]
 #[ruma_enum(rename_all = "snake_case")]