Send email on crate owner invitation

If the recipient of a crate ownership invitation has a verified email address, they will be sent an email indicating that a specified user has invited them to become an owner of a named crate. Only sends the email on the first instance of an invitation.

Author: nkanderson

src/email.rs

@@ -86,6 +86,23 @@ https://crates.io/confirm/{}",
     send_email(email, subject, &body)
 }
 
+/// Attempts to send a crate owner invitation email. Swallows all errors.
+///
+/// Whether or not the email is sent, the invitation entry will be created in
+/// the database and the user will see the invitation when they visit
+/// https://crates.io/me/pending-invites/.
+pub fn send_owner_invite_email(email: &str, user_name: &str, crate_name: &str) {
+    let subject = "Please confirm crate ownership";
+    let body = format!(
+        "{} has invited you to become an owner of the crate {}!\n
+Please visit https://crates.io/me/pending-invites to accept or reject
+this invitation.",
+        user_name, crate_name
+    );
+
+    let _ = send_email(email, subject, &body);
+}
+
 fn send_email(recipient: &str, subject: &str, body: &str) -> CargoResult<()> {
     let mailgun_config = init_config_vars();
     let email = build_email(recipient, subject, body, &mailgun_config)?;

src/models/krate.rs

@@ -7,11 +7,12 @@ use indexmap::IndexMap;
 use url::Url;
 
 use crate::app::App;
+use crate::email;
 use crate::util::{human, CargoResult};
 
 use crate::models::{
-    Badge, Category, CrateOwner, Keyword, NewCrateOwnerInvitation, Owner, OwnerKind,
-    ReverseDependency, User, Version,
+    Badge, Category, CrateOwner, CrateOwnerInvitation, Keyword, NewCrateOwnerInvitation, Owner,
+    OwnerKind, ReverseDependency, User, Version,
 };
 use crate::views::{EncodableCrate, EncodableCrateLinks};
 
@@ -427,14 +428,28 @@ impl Crate {
         match owner {
             // Users are invited and must accept before being added
             owner @ Owner::User(_) => {
-                insert_into(crate_owner_invitations::table)
+                let maybe_inserted = insert_into(crate_owner_invitations::table)
                     .values(&NewCrateOwnerInvitation {
                         invited_user_id: owner.id(),
                         invited_by_user_id: req_user.id,
                         crate_id: self.id,
                     })
                     .on_conflict_do_nothing()
-                    .execute(conn)?;
+                    .get_result::<CrateOwnerInvitation>(conn)
+                    .optional()?;
+
+                if maybe_inserted.is_some() {
+                    if let Owner::User(user) = &owner {
+                        if let Ok(Some(email)) = user.verified_email(&conn) {
+                            email::send_owner_invite_email(
+                                &email.as_str(),
+                                &req_user.gh_login.as_str(),
+                                &self.name.as_str(),
+                            );
+                        }
+                    }
+                }
+
                 Ok(format!(
                     "user {} has been invited to be an owner of crate {}",
                     owner.login(),