feat(admin): Add resolver cache flush command

This command allows an admin to flush a specific server
from the resolver caches or flush the whole cache.

docs/reference/admin/query.md

@@ -112,6 +112,19 @@ Query the destinations cache
 
 Query the overrides cache
 
+### `!admin query resolver flush-cache`
+
+Flush a given server from the resolver caches or flush them completely
+
+* Examples:
+  * Flush a specific server:
+
+    `!admin query resolver flush-cache matrix.example.com`
+
+  * Flush all resolver caches completely:
+
+    `!admin query resolver flush-cache --all`
+
 ## `!admin query pusher`
 
 pusher service

src/admin/query/resolver.rs

@@ -1,5 +1,5 @@
 use clap::Subcommand;
-use conduwuit::{Result, utils::time};
+use conduwuit::{Err, Result, utils::time};
 use futures::StreamExt;
 use ruma::OwnedServerName;
 
@@ -7,6 +7,7 @@ use crate::{admin_command, admin_command_dispatch};
 
 #[admin_command_dispatch]
 #[derive(Debug, Subcommand)]
+#[allow(clippy::enum_variant_names)]
 /// Resolver service and caches
 pub enum ResolverCommand {
 	/// Query the destinations cache
@@ -18,6 +19,14 @@ pub enum ResolverCommand {
 	OverridesCache {
 		name: Option<String>,
 	},
+
+	/// Flush a specific server from the resolver caches or everything
+	FlushCache {
+		name: Option<OwnedServerName>,
+
+		#[arg(short, long)]
+		all: bool,
+	},
 }
 
 #[admin_command]
@@ -69,3 +78,18 @@ async fn overrides_cache(&self, server_name: Option<String>) -> Result {
 
 	Ok(())
 }
+
+#[admin_command]
+async fn flush_cache(&self, name: Option<OwnedServerName>, all: bool) -> Result {
+	if all {
+		self.services.resolver.cache.clear().await;
+		writeln!(self, "Resolver caches cleared!").await
+	} else if let Some(name) = name {
+		self.services.resolver.cache.del_destination(&name);
+		self.services.resolver.cache.del_override(&name);
+		self.write_str(&format!("Cleared {name} from resolver caches!"))
+			.await
+	} else {
+		Err!("Missing name. Supply a name or use --all to flush the whole cache.")
+	}
+}