Add QUICHE_EXPORT to Oblivious HTTP helper functions.

This adds the QUICHE_EXPORT annotation to Check*Id and ObliviousHttp*IdToString functions in oblivious_http_header_key_config.h. This resolves linking errors in component builds, such as in Chromium.

No change to GFE. No functional change in component builds.

PiperOrigin-RevId: 952046153

quiche/oblivious_http/common/oblivious_http_header_key_config.h

diff --git a/quiche/oblivious_http/common/oblivious_http_header_key_config.h b/quiche/oblivious_http/common/oblivious_http_header_key_config.h
index 8517e29..4376e49 100644
--- a/quiche/oblivious_http/common/oblivious_http_header_key_config.h
+++ b/quiche/oblivious_http/common/oblivious_http_header_key_config.h
@@ -22,9 +22,10 @@
 
 // Provide access to the underlying EVP_HPKE_KEM, EVP_HPKE_KDF, and
 // EVP_HPKE_AEAD if they are supported.
-absl::StatusOr<const EVP_HPKE_KEM*> CheckKemId(uint16_t kem_id);
-absl::StatusOr<const EVP_HPKE_KDF*> CheckKdfId(uint16_t kdf_id);
-absl::StatusOr<const EVP_HPKE_AEAD*> CheckAeadId(uint16_t aead_id);
+QUICHE_EXPORT absl::StatusOr<const EVP_HPKE_KEM*> CheckKemId(uint16_t kem_id);
+QUICHE_EXPORT absl::StatusOr<const EVP_HPKE_KDF*> CheckKdfId(uint16_t kdf_id);
+QUICHE_EXPORT absl::StatusOr<const EVP_HPKE_AEAD*> CheckAeadId(
+    uint16_t aead_id);
 
 class QUICHE_EXPORT ObliviousHttpHeaderKeyConfig {
  public:
@@ -276,9 +277,9 @@
 };
 
 // Human-readable strings suitable for logging.
-std::string ObliviousHttpKemIdToString(uint16_t kem_id);
-std::string ObliviousHttpKdfIdToString(uint16_t kdf_id);
-std::string ObliviousHttpAeadIdToString(uint16_t aead_id);
+QUICHE_EXPORT std::string ObliviousHttpKemIdToString(uint16_t kem_id);
+QUICHE_EXPORT std::string ObliviousHttpKdfIdToString(uint16_t kdf_id);
+QUICHE_EXPORT std::string ObliviousHttpAeadIdToString(uint16_t aead_id);
 
 }  // namespace quiche