docs: fix outdated example of specifying a custom unix socket

This should have happened automatically when Cargo.toml was updated

Cargo.lock

@@ -376,7 +376,7 @@ dependencies = [
 
 [[package]]
 name = "cup"
-version = "3.3.0"
+version = "3.4.1"
 dependencies = [
  "bollard",
  "chrono",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cup"
-version = "3.4.0"
+version = "3.4.1"
 edition = "2021"
 
 [dependencies]

docs/src/content/docs/configuration/index.mdx

@@ -20,7 +20,7 @@ Sometimes, there may be a need to specify a custom docker socket. Cup provides t
 For example, if using Podman, you might do
 
 ```bash
-$ cup -s /run/user/1000/podman/podman.sock check
+$ cup -s unix:///run/user/1000/podman/podman.sock check
 ```
 
 This option is also available in the configuration file and it's best to put it there.

docs/src/content/docs/configuration/socket.mdx

@@ -4,7 +4,7 @@ If you need to specify a custom Docker socket (e.g. because you're using Podman)
 
 ```jsonc
 {
-  "socket": "/run/user/1000/podman/podman.sock"
+  "socket": "unix:///run/user/1000/podman/podman.sock"
   // Other options
 }
 ```
@@ -16,4 +16,4 @@ You can also specify a TCP socket if you're using a remote Docker host or a [pro
   "socket": "tcp://localhost:2375"
   // Other options
 }
-```
+```

src/config.rs

@@ -1,5 +1,6 @@
 use rustc_hash::FxHashMap;
 use serde::Deserialize;
+use serde::Deserializer;
 use std::env;
 use std::mem;
 use std::path::PathBuf;
@@ -64,6 +65,7 @@ pub struct Config {
     pub agent: bool,
     pub ignore_update_type: UpdateType,
     pub images: ImageConfig,
+    #[serde(deserialize_with = "empty_as_none")]
     pub refresh_interval: Option<String>,
     pub registries: FxHashMap<String, RegistryConfig>,
     pub servers: FxHashMap<String, String>,
@@ -151,3 +153,15 @@ impl Default for Config {
         Self::new()
     }
 }
+
+fn empty_as_none<'de, D>(deserializer: D) -> Result<Option<String>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let s = String::deserialize(deserializer)?;
+    if s.is_empty() {
+        Ok(None)
+    } else {
+        Ok(Some(s))
+    }
+}