fix(dht): sets file default for DHT db (#4030)

Description
---
- sets database file default for DHT db on the p2p level

Motivation and Context
---
Default was using ephemeral memory db

How Has This Been Tested?
---
Manually, base node does not emit error on linux

base_layer/p2p/src/config.rs

@@ -32,7 +32,7 @@ use tari_common::{
     SubConfigPath,
 };
 use tari_comms::multiaddr::Multiaddr;
-use tari_comms_dht::DhtConfig;
+use tari_comms_dht::{DbConnectionUrl, DhtConfig};
 
 use crate::{transport::TransportConfig, DEFAULT_DNS_NAME_SERVER};
 
@@ -131,7 +131,10 @@ impl Default for P2pConfig {
             max_concurrent_inbound_tasks: 50,
             max_concurrent_outbound_tasks: 100,
             outbound_buffer_size: 100,
-            dht: Default::default(),
+            dht: DhtConfig {
+                database_url: DbConnectionUrl::file("dht.sqlite"),
+                ..Default::default()
+            },
             allow_test_addresses: false,
             listener_liveness_max_sessions: 0,
             listener_liveness_allowlist_cidrs: StringList::default(),

comms/dht/src/storage/connection.rs

@@ -52,6 +52,10 @@ pub enum DbConnectionUrl {
 }
 
 impl DbConnectionUrl {
+    pub fn file<P: AsRef<Path>>(path: P) -> Self {
+        DbConnectionUrl::File(path.as_ref().to_path_buf())
+    }
+
     pub fn to_url_string(&self) -> String {
         use DbConnectionUrl::{File, Memory, MemoryShared};
         match self {