feat: Add BE changes for captain pdf support for faq generation (#12113)

spec/fixtures/files/sample.pdf

@@ -0,0 +1,32 @@
+%PDF-1.4
+1 0 obj
+<< /Type /Catalog /Pages 2 0 R >>
+endobj
+2 0 obj
+<< /Type /Pages /Kids [3 0 R] /Count 1 >>
+endobj
+3 0 obj
+<< /Type /Page /Parent 2 0 R /Resources << /Font << /F1 << /Type /Font /Subtype /Type1 /BaseFont /Arial >> >> >> /MediaBox [0 0 612 792] /Contents 4 0 R >>
+endobj
+4 0 obj
+<< /Length 44 >>
+stream
+BT
+/F1 12 Tf
+100 700 Td
+(Sample PDF) Tj
+ET
+endstream
+endobj
+xref
+0 5
+0000000000 65535 f 
+0000000009 00000 n 
+0000000058 00000 n 
+0000000115 00000 n 
+0000000274 00000 n 
+trailer
+<< /Size 5 /Root 1 0 R >>
+startxref
+362
+%%EOF