Clarify requirements of the Contexts SPI interface

Author: manovotn

api/src/main/java/org/jboss/cdi/tck/spi/Contexts.java

@@ -34,14 +34,22 @@ public interface Contexts<T extends Context> {
     public static final String PROPERTY_NAME = Contexts.class.getName();
 
     /**
-     * Sets the specified context as active
+     * Sets the specified context as active.
+     * <p>
+     * If the context was previously set as inactive via {@link  #setInactive(Context)}, this method is expected to
+     * restore the state of the context, including all contextual instances that were previously in it.
+     * <p>
+     * If the context wasn't previously set as inactive, a new context is created and activated.
      *
      * @param context The context to set active
      */
     public void setActive(T context);
 
     /**
-     * Sets the specified context as inactive
+     * Sets the specified context as inactive; this operation does not destroy contextual instances.
+     * <p>
+     * Implementations need to store the context state as subsequent invocations of {@link #setActive(Context)} may
+     * attempt to restore the context.
      *
      * @param context The context to set inactive
      */