Add allowedInKey(char) method to check character validity for keys

key/src/main/java/net/kyori/adventure/key/Key.java

@@ -225,21 +225,32 @@ static boolean parseableValue(final @NotNull String value) {
   }
 
   /**
-   * Checks if {@code value} is a valid character in a namespace.
+   * Checks if {@code character} is a valid character in a key.
    *
    * @param character the character to check
-   * @return {@code true} if {@code value} is a valid character in a namespace, {@code false} otherwise
+   * @return {@code true} if {@code character} is a valid character in a key, {@code false} otherwise
+   * @since 4.25.0
+   */
+  static boolean allowedInKey(final char character) {
+    return KeyImpl.allowedInKey(character);
+  }
+
+  /**
+   * Checks if {@code character} is a valid character in a namespace.
+   *
+   * @param character the character to check
+   * @return {@code true} if {@code character} is a valid character in a namespace, {@code false} otherwise
    * @since 4.12.0
    */
   static boolean allowedInNamespace(final char character) {
     return KeyImpl.allowedInNamespace(character);
   }
 
   /**
-   * Checks if {@code value} is a valid character in a value.
+   * Checks if {@code character} is a valid character in a value.
    *
    * @param character the character to check
-   * @return {@code true} if {@code value} is a valid character in a value, {@code false} otherwise
+   * @return {@code true} if {@code character} is a valid character in a value, {@code false} otherwise
    * @since 4.12.0
    */
   static boolean allowedInValue(final char character) {

key/src/main/java/net/kyori/adventure/key/KeyImpl.java

@@ -66,6 +66,10 @@ private static void checkError(final String name, final String checkPart, final
     }
   }
 
+  static boolean allowedInKey(final char character) {
+    return character == ':' || allowedInNamespace(character) || allowedInValue(character);
+  }
+
   static boolean allowedInNamespace(final char character) {
     return character == '_' || character == '-' || (character >= 'a' && character <= 'z') || (character >= '0' && character <= '9') || character == '.';
   }