Add a helper function to verify webhook requests

The new `request::verified()` takes POST params as a string as does all
the work needed to call `paddle::verify_signature()`.

This involves extracting the `p_signature` POST parameter to get the
signature, and getting the public key PEM.

Change `params::parse()` to return a
`BTreeMap<Cow<'a, str>, Cow<'a, str>>` instead of `String` keys &
values. This is because `paddle::verify_signature()` needs a `(<&str,
&str)` iterator. Actually, it still doesn't solve the problem because
the types don't match. We need to modify the input type of
`verify_signature()`, but at least this change gives us references.

Make `params` private to the crate because we no longer need to use it
in `main()`.

1 files changed, 3 insertions, 2 deletions

diff --git a/license-generator/src/params.rs b/license-generator/src/params.rs
index 80136c2..1b234e7 100644
--- a/license-generator/src/params.rs
+++ b/license-generator/src/params.rs
@@ -1,9 +1,10 @@
+use std::borrow::Cow;
 use std::collections::BTreeMap;
 
 use url::form_urlencoded;
 
-pub fn parse(params: &str) -> BTreeMap<String, String> {
-    let iter = form_urlencoded::parse(params.as_bytes()).into_owned();
+pub(crate) fn parse<'a>(params: &'a str) -> BTreeMap<Cow<'a, str>, Cow<'a, str>> {
+    let iter = form_urlencoded::parse(params.as_bytes());
     let mut dict = BTreeMap::new();
 
     for (key, value) in iter {