Update content decoding and validation logic

- Changed `PageNumber` in `Chunk` to nullable `int?` in `IContentDecoder` and updated related logic in `TextContentDecoder`.
- Revised citation rules in `ChatService` for stricter placement and formatting.
- Introduced `QuestionValidator` class with validation rules for `Question` model's `Text` property.

SqlDatabaseVectorSearch/ContentDecoders/IContentDecoder.cs

@@ -5,4 +5,4 @@ public interface IContentDecoder
     Task<IEnumerable<Chunk>> DecodeAsync(Stream stream, string contentType, CancellationToken cancellationToken = default);
 }
 
-public record class Chunk(int PageNumber, int IndexOnPage, string Content);
+public record class Chunk(int? PageNumber, int IndexOnPage, string Content);

SqlDatabaseVectorSearch/ContentDecoders/TextContentDecoder.cs

@@ -12,6 +12,6 @@ public class TextContentDecoder(IServiceProvider serviceProvider) : IContentDeco
         var content = await readStream.ReadToEndAsync(cancellationToken);
 
         var paragraphs = textChunker.Split(content);
-        return paragraphs.Select((text, index) => new Chunk(1, index, text)).ToList();
+        return paragraphs.Select((text, index) => new Chunk(null, index, text)).ToList();
     }
 }

SqlDatabaseVectorSearch/Services/ChatService.cs

@@ -127,23 +127,12 @@ public class ChatService(IChatCompletionService chatCompletionService, Tokenizer
             Never answer questions that are not related to this chat.
             You must answer in the same language as the user's question.
 
-            IMPORTANT - CITATION PLACEMENT AND LENGTH:
             The quote in each <citation> MUST be MAXIMUM 5 words, taken word-for-word from the search result. If the quote is longer than 5 words, your answer is INVALID.
             When you find an answer, you MUST place ALL citations ONLY at the very end of your response, never inside or between sentences.
-            First provide your complete answer, then add a blank line, then list all citations.
+            First provide your complete answer, then list all citations.
             
             Use this XML format for citations:
             <citation document-id='document_id' chunk-id='chunk_id' filename='string' page-number='1'>exact quote here</citation>
-
-            STRICT RULES for citations:
-            - Citations MUST NEVER appear inside, before, or between sentences of your answer. They MUST be grouped together ONLY at the end, after a blank line.
-            - If you include citations anywhere except at the end, your answer is WRONG and INVALID.
-            - Always include the citation(s) if there are results. If you don't know the answer, do NOT include citations.
-            - The quote must be max 5 words, taken word-for-word from the search result, and is the basis for why the citation is relevant. If the quote is longer than 5 words, your answer is INVALID.
-            - Do NOT refer to the presence of citations; just emit these tags right at the end, with no surrounding text.
-            - The citations must always be in a list at the end of the response, one after the other. Never add the citations between the actual response text or inside sentences.
-            - Do NOT add any text after the citations.
-            - ALWAYS leave a blank line between your answer and the first citation.
             """);
 
         var prompt = new StringBuilder($"""

SqlDatabaseVectorSearch/Validations/QuestionValidator.cs

@@ -1,7 +1,7 @@
 using FluentValidation;
 using SqlDatabaseVectorSearch.Models;
 
-namespace SqlDatabaseVectorSearch.Validators;
+namespace SqlDatabaseVectorSearch.Validations;
 
 public class QuestionValidator : AbstractValidator<Question>
 {