port `DocumentKey` to non-container types of `Model/*` (#930)

* naively remove FSTPath import and source/test files.

* port FieldPath, part I

* port FieldPath, part II

* port ResourcePath, part I

* port ResourcePath, part II

* the grand commit to fix build errors

* use testutil:: helper instead of those from FSTHelpers

* fix test and lint

* use c_str in errmsg directly

* fix

* fix

* make code clean

* fix integration test I missed

* fix to avoid naming collision in preprocessor

* address changes

* address changes

* address changes

* fix: fieldMask are actually shared with different context.

* address changes

* add converter function between two DocumentKey implementations

* add unit test

* address changes

* fix lint

* using DocumentKey in model except for the container types `FSTDocumentDictionary`, `FSTDocumentKeySet`, and  `FSTDocumentVersionDictionary`

* change other place w.r.t. the use of `DocumentKey` in model

* update parameter of test helpers from NSString to string_view

* revert a temporary change used in debug

* address changes

1 files changed, 3 insertions, 3 deletions

diff --git a/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm b/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm
index c86318d..97f0ef1 100644
--- a/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm
+++ b/Firestore/Source/Local/FSTLevelDBRemoteDocumentCache.mm
@@ -111,7 +111,7 @@ static ReadOptions StandardReadOptions() {
   for (; it->Valid() && [currentKey decodeKey:it->key()]; it->Next()) {
     FSTMaybeDocument *maybeDoc =
         [self decodedMaybeDocument:it->value() withKey:currentKey.documentKey];
-    if (!query.path.IsPrefixOf(maybeDoc.key.path)) {
+    if (!query.path.IsPrefixOf(maybeDoc.key.path())) {
       break;
     } else if ([maybeDoc isKindOfClass:[FSTDocument class]]) {
       results = [results dictionaryBySettingObject:(FSTDocument *)maybeDoc forKey:maybeDoc.key];
@@ -143,8 +143,8 @@ static ReadOptions StandardReadOptions() {
 
   FSTMaybeDocument *maybeDocument = [self.serializer decodedMaybeDocument:proto];
   FSTAssert([maybeDocument.key isEqualToKey:documentKey],
-            @"Read document has key (%@) instead of expected key (%@).", maybeDocument.key,
-            documentKey);
+            @"Read document has key (%s) instead of expected key (%@).",
+            maybeDocument.key.ToString().c_str(), documentKey);
   return maybeDocument;
 }