Add more documentation

Author: linus-mullvad

src/policy/builtin.rs

@@ -5,6 +5,10 @@ use super::Policy;
 
 /// A built-in policy with a given name.
 ///
+/// The user facing name of this policy can be accessed via the public `name` field.
+/// This struct implements `Deref<Target=Policy>`, so using it as a [`Policy`] becomes
+/// transparent.
+///
 /// This policy is parsed and lazily initialized on first use.
 pub struct BuiltInPolicy {
     /// The user-friendly name of the built-in policy.

src/policy/mod.rs

@@ -11,6 +11,8 @@ pub use parsing::ParsePolicyError;
 ///
 /// The Sigsum policy dictates if a signed tree head is considered valid (and by extension, if a
 /// Sigsum signature is valid).
+///
+/// This library contains a bunch of built in policies, ready for use in [`builtin`].
 #[derive(Debug, Eq, PartialEq)]
 pub struct Policy {
     // logs keeps the list of log keys and URLs indexed by keyhash.