Add authentication from upstream providers (#107)

Let BasicOIDC delegate authentication to upstream providers (Google, GitHub, GitLab, Keycloak...)

Reviewed-on: #107

src/data/provider.rs

@@ -0,0 +1,89 @@
+use crate::data::entity_manager::EntityManager;
+use crate::data::login_redirect::LoginRedirect;
+use crate::utils::string_utils::apply_env_vars;
+
+#[derive(Clone, Debug, serde::Serialize, serde::Deserialize, Eq, PartialEq)]
+pub struct ProviderID(pub String);
+
+#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
+pub struct Provider {
+    /// The ID of the provider
+    pub id: ProviderID,
+
+    /// The human-readable name of the client
+    pub name: String,
+
+    /// A logo presented to the users of the provider
+    pub logo: String,
+
+    /// The registration id of BasicOIDC on the provider
+    pub client_id: String,
+
+    /// The registration secret of BasicOIDC on the provider
+    pub client_secret: String,
+
+    /// Specify the URL of the OpenID configuration URL
+    ///
+    /// (.well-known/openid-configuration endpoint)
+    pub configuration_url: String,
+}
+
+impl Provider {
+    /// Get URL-encoded provider id
+    pub fn id_encoded(&self) -> String {
+        urlencoding::encode(&self.id.0).to_string()
+    }
+
+    /// Get the URL where the logo can be located
+    pub fn logo_url(&self) -> &str {
+        match self.logo.as_str() {
+            "gitea" => "/assets/img/brands/gitea.svg",
+            "gitlab" => "/assets/img/brands/gitlab.svg",
+            "github" => "/assets/img/brands/github.svg",
+            "microsoft" => "/assets/img/brands/microsoft.svg",
+            "google" => "/assets/img/brands/google.svg",
+            s => s,
+        }
+    }
+
+    /// Get the URL to use to login with the provider
+    pub fn login_url(&self, redirect_url: &LoginRedirect) -> String {
+        format!(
+            "/login_with_prov?id={}&redirect={}",
+            self.id_encoded(),
+            redirect_url.get_encoded()
+        )
+    }
+}
+
+impl PartialEq for Provider {
+    fn eq(&self, other: &Self) -> bool {
+        self.id.eq(&other.id)
+    }
+}
+
+impl Eq for Provider {}
+
+pub type ProvidersManager = EntityManager<Provider>;
+
+impl EntityManager<Provider> {
+    pub fn find_by_id(&self, u: &ProviderID) -> Option<Provider> {
+        for entry in self.iter() {
+            if entry.id.eq(u) {
+                return Some(entry.clone());
+            }
+        }
+        None
+    }
+
+    pub fn apply_environment_variables(&mut self) {
+        for c in self.iter_mut() {
+            c.id = ProviderID(apply_env_vars(&c.id.0));
+            c.name = apply_env_vars(&c.name);
+            c.logo = apply_env_vars(&c.logo);
+            c.client_id = apply_env_vars(&c.client_id);
+            c.client_secret = apply_env_vars(&c.client_secret);
+            c.configuration_url = apply_env_vars(&c.configuration_url);
+        }
+    }
+}