Use more string_view as suggested by clang-tidy 23

cpp/tests/poppler-dump.cpp

diff --git a/cpp/tests/poppler-dump.cpp b/cpp/tests/poppler-dump.cpp
index caaee3c..3717a5e 100644
--- a/cpp/tests/poppler-dump.cpp
+++ b/cpp/tests/poppler-dump.cpp
@@ -137,7 +137,7 @@
     return ret;
 }
 
-static std::string out_page_orientation(poppler::page::orientation_enum o)
+static std::string_view out_page_orientation(poppler::page::orientation_enum o)
 {
     switch (o) {
     case poppler::page::landscape:
@@ -152,7 +152,7 @@
     return "<unknown orientation>";
 }
 
-static std::string out_font_info_type(poppler::font_info::type_enum t)
+static std::string_view out_font_info_type(poppler::font_info::type_enum t)
 {
 #define OUT_FONT_TYPE(thetype)                                                                                                                                                                                                                 \
     case poppler::font_info::thetype:                                                                                                                                                                                                          \

poppler/CryptoSignBackend.cc

diff --git a/poppler/CryptoSignBackend.cc b/poppler/CryptoSignBackend.cc
index e24d2d0..1038f09 100644
--- a/poppler/CryptoSignBackend.cc
+++ b/poppler/CryptoSignBackend.cc
@@ -35,7 +35,7 @@
     return CryptoSign::SignatureType::unknown_signature_type;
 }
 
-std::string toStdString(SignatureType type)
+std::string_view toStdString(SignatureType type)
 {
     switch (type) {
     case CryptoSign::SignatureType::unsigned_signature_field:

poppler/CryptoSignBackend.h

diff --git a/poppler/CryptoSignBackend.h b/poppler/CryptoSignBackend.h
index bad717a..1261b41 100644
--- a/poppler/CryptoSignBackend.h
+++ b/poppler/CryptoSignBackend.h
@@ -37,7 +37,7 @@
 
 SignatureType signatureTypeFromString(std::string_view data);
 
-std::string toStdString(SignatureType type);
+std::string_view toStdString(SignatureType type);
 
 // experiments seems to say that this is a bit above
 // what we have seen in the wild, and much larger than