feat: Implement and use LedgerCacheInterface (#1955)

For #1200

tests/unit/feed/BookChangesFeedTests.cpp

@@ -30,6 +30,7 @@
 #include <vector>
 
 using namespace feed::impl;
+using namespace data;
 
 namespace {
 

tests/unit/feed/SubscriptionManagerTests.cpp

@@ -58,6 +58,7 @@ constexpr auto kLEDGER_HASH = "4BC50C9B0D8515D3EAAE1E74B29A95804346C491EE1A95BF2
 namespace json = boost::json;
 using namespace feed;
 using namespace feed::impl;
+using namespace data;
 
 template <class Execution>
 class SubscriptionManagerBaseTest : public util::prometheus::WithPrometheus, public MockBackendTest {

tests/unit/feed/TransactionFeedTests.cpp

@@ -45,6 +45,8 @@
 #include <memory>
 #include <vector>
 
+using namespace data;
+
 namespace {
 
 constexpr auto kACCOUNT1 = "rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn";