admin api: base infrastructure for local endpoints

admin api: rename EndpointHandler into RequestHandler to avoid confusion with RPC

wip: infrastructure for local api calls

admin api: fix things

admin api: first local endpoint to work with new scheme

admin api: implement SetWorkerVariable

src/api/admin/worker.rs

@@ -0,0 +1,50 @@
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+
+use garage_model::garage::Garage;
+
+use crate::api::*;
+use crate::error::Error;
+use crate::{Admin, RequestHandler};
+
+#[async_trait]
+impl RequestHandler for LocalGetWorkerVariableRequest {
+	type Response = LocalGetWorkerVariableResponse;
+
+	async fn handle(
+		self,
+		garage: &Arc<Garage>,
+		_admin: &Admin,
+	) -> Result<LocalGetWorkerVariableResponse, Error> {
+		let mut res = HashMap::new();
+		if let Some(k) = self.variable {
+			res.insert(k.clone(), garage.bg_vars.get(&k)?);
+		} else {
+			let vars = garage.bg_vars.get_all();
+			for (k, v) in vars.iter() {
+				res.insert(k.to_string(), v.to_string());
+			}
+		}
+		Ok(LocalGetWorkerVariableResponse(res))
+	}
+}
+
+#[async_trait]
+impl RequestHandler for LocalSetWorkerVariableRequest {
+	type Response = LocalSetWorkerVariableResponse;
+
+	async fn handle(
+		self,
+		garage: &Arc<Garage>,
+		_admin: &Admin,
+	) -> Result<LocalSetWorkerVariableResponse, Error> {
+		garage.bg_vars.set(&self.variable, &self.value)?;
+
+		Ok(LocalSetWorkerVariableResponse {
+			variable: self.variable,
+			value: self.value,
+		})
+	}
+}