added configurable custom prompt

This makes it easier to add to the existing internal prompt instead of
completely overwriting it using the localization mechanism.

conf/default.php

@@ -11,6 +11,8 @@
 $conf['embedmodel'] = 'OpenAI text-embedding-ada-002';
 $conf['storage'] = 'SQLite';
 
+$conf['customprompt'] = '';
+
 $conf['openai_apikey']    = '';
 $conf['openai_org']    = '';
 

conf/metadata.php

@@ -18,6 +18,8 @@
     )
 );
 
+$meta['customprompt'] = array();
+
 $meta['openai_apikey'] = array('password');
 $meta['openai_org'] = array('string');
 

helper.php

@@ -202,6 +202,7 @@ public function askQuestion($question, $history = [], $contextQuestion = '')
             $prompt = $this->getPrompt('question', [
                 'context' => $context,
                 'question' => $question,
+                'customprompt' => $this->getConf('customprompt'),
             ]);
         } else {
             $prompt = $this->getPrompt('noanswer', [

lang/en/question.prompt

@@ -1,4 +1,4 @@
-Your Task: Use the following documents as context to answer the users question. If you don't know the answer, just say that you don't know, don't try to make up an answer. {{LANGUAGE}}
+Your Task: Use the following documents as context to answer the users question. If you don't know the answer, just say that you don't know, don't try to make up an answer. {{LANGUAGE}} {{CUSTOMPROMPT}}
 
 ----------------
 {{CONTEXT}}

lang/en/settings.php

@@ -10,7 +10,7 @@
 $lang['rephrasemodel'] = 'The 🧠 model to use for rephrasing questions. Configure required credentials below.';
 $lang['embedmodel'] = 'The 🧠 model to use for text embedding. Configure required credentials below.<br>🔄 You need to rebuild the vector storage when changing this setting.';
 $lang['storage'] = 'Which 📥 vector storage to use. Configure required credentials below.<br>🔄 You need to rebuild the vector storage when changing this setting.';
-
+$lang['customprompt'] = 'A custom prompt that is added to the prompt used by this plugin when querying the AI model. For consistency, it should be in English.';
 
 $lang['openai_apikey'] = '🧠 <b>OpenAI</b> API key';
 $lang['openai_org'] = '🧠 <b>OpenAI</b> Organization ID (if any)';