Add notifications for target maintainers (#10)

This adds a feature where maintainers can add themselves to an array in the source to receive notifications whenever the target fails.

The way this works is via GitHub, I created a new repository https://github.com/Noratrieb/does-it-build-notifications where an app will create issues that ping the respective users. This is the easiest option for me and also fits nicely into people's workflows on GitHub.

Whenever a target fails, an issue is created for it. This issue is kept open (with a new comment every day that it continues to fail), and then closed when the target builds again.

src/github.rs

@@ -0,0 +1,39 @@
+use color_eyre::{eyre::Context, Result};
+use octocrab::issues;
+
+pub struct GitHubClient {
+    pub send_pings: bool,
+    owner: String,
+    repo: String,
+    pub client: octocrab::Octocrab,
+}
+
+impl GitHubClient {
+    pub async fn new(
+        send_pings: bool,
+        client: octocrab::Octocrab,
+        owner: String,
+        repo: String,
+    ) -> Result<Self> {
+        let installation = client
+            .apps()
+            .get_repository_installation(&owner, &repo)
+            .await
+            .wrap_err_with(|| format!("getting installation for {owner}/{repo}"))?;
+
+        let client = client
+            .installation(installation.id)
+            .wrap_err("getting client for installation")?;
+
+        Ok(Self {
+            send_pings,
+            owner,
+            repo,
+            client,
+        })
+    }
+
+    pub fn issues(&self) -> issues::IssueHandler<'_> {
+        self.client.issues(&self.owner, &self.repo)
+    }
+}