doc: amend description to point to CertificateParams for additional explanation

Author: mcr

rcgen/src/csr.rs

@@ -37,6 +37,11 @@ impl PublicKeyData for PublicKey {
 }
 
 /// A certificate signing request (CSR) that can be encoded to PEM or DER.
+///
+/// A new certificate signing request is created by filling out a CertificateParams object
+/// and then calling serialize_request() or serialize_request_with_attributes() with a
+/// KeyPair (or other SigningKey capable trait).
+///
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct CertificateSigningRequest {
 	pub(crate) der: CertificateSigningRequestDer<'static>,