Allow for prompt caching to work by using baibot_conversation_start_time_utc instead of baibot_now_utc

This patch introduces a new `baibot_conversation_start_time_utc`
variable which indicates the time the conversation got started.

Using `baibot_now_utc` is still possible, but given that the current
time is a moving target, its use is in conflict with prompt caching.

Because the new `baibot_conversation_start_time_utc` prompt variable
is a more reasonable default, we're now using it in all sample configs.

src/conversation/matrix/utils/tests.rs

@@ -1,3 +1,5 @@
+use chrono::{TimeZone, Utc};
+
 use mxlink::matrix_sdk::ruma::OwnedUserId;
 
 use crate::conversation::matrix::{
@@ -11,11 +13,14 @@ fn is_message_from_allowed_sender() {
     let allowed_user_id = OwnedUserId::try_from("@user.someone:example.com").unwrap();
     let unallowed_user_id = OwnedUserId::try_from("@another:example.com").unwrap();
 
+    let timestamp = Utc.with_ymd_and_hms(2024, 9, 20, 18, 34, 15).unwrap();
+
     let bot_message = MatrixMessage {
         sender_id: bot_user_id.to_owned(),
         message_type: MatrixMessageType::Text,
         message_text: "Hello!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let allowed_user_message = MatrixMessage {
@@ -23,6 +28,7 @@ fn is_message_from_allowed_sender() {
         message_type: MatrixMessageType::Text,
         message_text: "Hello!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let unallowed_user_message = MatrixMessage {
@@ -30,6 +36,7 @@ fn is_message_from_allowed_sender() {
         message_type: MatrixMessageType::Text,
         message_text: "Hello!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let parsed_regex = match mxidwc::parse_pattern("@user.*:example.com") {
@@ -77,11 +84,14 @@ async fn process_matrix_messages() {
     let allowed_user_id = OwnedUserId::try_from("@user.someone:example.com").unwrap();
     let unallowed_user_id = OwnedUserId::try_from("@another:example.com").unwrap();
 
+    let timestamp = Utc.with_ymd_and_hms(2024, 9, 20, 18, 34, 15).unwrap();
+
     let allowed_user_message = MatrixMessage {
         sender_id: allowed_user_id.to_owned(),
         message_type: MatrixMessageType::Text,
         message_text: "Hello from the user!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let allowed_user_message_with_prefix = MatrixMessage {
@@ -89,6 +99,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: "!bai Hello from the user!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let allowed_user_message_with_prefix_no_space = MatrixMessage {
@@ -96,6 +107,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: "!baiHello from the user!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let allowed_user_message_with_prefix_full_width_space = MatrixMessage {
@@ -103,6 +115,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: "!bai　Hello from the user!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let bot_message = MatrixMessage {
@@ -110,6 +123,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: "Hello from the bot!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let allowed_user_message_with_bot_mention = MatrixMessage {
@@ -117,6 +131,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: "@baibot: Hello from the user!".to_owned(),
         mentioned_users: vec![bot_user_id.to_owned()],
+        timestamp,
     };
 
     // The message text is the same as above - it mentions the bot, but the actually-mentioned user is another user.
@@ -125,6 +140,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: allowed_user_message_with_bot_mention.message_text.clone(),
         mentioned_users: vec![allowed_user_id.to_owned()],
+        timestamp,
     };
 
     let unallowed_user_message = MatrixMessage {
@@ -132,6 +148,7 @@ async fn process_matrix_messages() {
         message_type: MatrixMessageType::Text,
         message_text: "Hello from an unallowed user!".to_owned(),
         mentioned_users: vec![],
+        timestamp,
     };
 
     let parsed_regex = match mxidwc::parse_pattern("@user.*:example.com") {