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

2 files changed, 9 insertions, 6 deletions

diff --git a/Firestore/Example/Tests/Util/FSTHelpers.h b/Firestore/Example/Tests/Util/FSTHelpers.h
index d86201b..d05c1f1 100644
--- a/Firestore/Example/Tests/Util/FSTHelpers.h
+++ b/Firestore/Example/Tests/Util/FSTHelpers.h
@@ -192,13 +192,13 @@ typedef int64_t FSTTestSnapshotVersion;
 FSTSnapshotVersion *FSTTestVersion(FSTTestSnapshotVersion version);
 
 /** A convenience method for creating docs for tests. */
-FSTDocument *FSTTestDoc(NSString *path,
+FSTDocument *FSTTestDoc(const absl::string_view path,
                         FSTTestSnapshotVersion version,
                         NSDictionary<NSString *, id> *data,
                         BOOL hasMutations);
 
 /** A convenience method for creating deleted docs for tests. */
-FSTDeletedDocument *FSTTestDeletedDoc(NSString *path, FSTTestSnapshotVersion version);
+FSTDeletedDocument *FSTTestDeletedDoc(const absl::string_view path, FSTTestSnapshotVersion version);
 
 /**
  * A convenience method for creating a document reference from a path string.
diff --git a/Firestore/Example/Tests/Util/FSTHelpers.mm b/Firestore/Example/Tests/Util/FSTHelpers.mm
index be02002..5751739 100644
--- a/Firestore/Example/Tests/Util/FSTHelpers.mm
+++ b/Firestore/Example/Tests/Util/FSTHelpers.mm
@@ -43,6 +43,7 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
+#include "Firestore/core/src/firebase/firestore/model/document_key.h"
 #include "Firestore/core/src/firebase/firestore/model/field_value.h"
 #include "Firestore/core/src/firebase/firestore/model/resource_path.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
@@ -51,6 +52,7 @@
 namespace util = firebase::firestore::util;
 namespace testutil = firebase::firestore::testutil;
 using firebase::firestore::model::DatabaseId;
+using firebase::firestore::model::DocumentKey;
 using firebase::firestore::model::FieldPath;
 using firebase::firestore::model::FieldValue;
 using firebase::firestore::model::ResourcePath;
@@ -148,19 +150,20 @@ FSTSnapshotVersion *FSTTestVersion(FSTTestSnapshotVersion versionMicroseconds) {
   return [FSTSnapshotVersion versionWithTimestamp:timestamp];
 }
 
-FSTDocument *FSTTestDoc(NSString *path,
+FSTDocument *FSTTestDoc(const absl::string_view path,
                         FSTTestSnapshotVersion version,
                         NSDictionary<NSString *, id> *data,
                         BOOL hasMutations) {
-  FSTDocumentKey *key = FSTTestDocKey(path);
+  DocumentKey key = testutil::Key(path);
   return [FSTDocument documentWithData:FSTTestObjectValue(data)
                                    key:key
                                version:FSTTestVersion(version)
                      hasLocalMutations:hasMutations];
 }
 
-FSTDeletedDocument *FSTTestDeletedDoc(NSString *path, FSTTestSnapshotVersion version) {
-  FSTDocumentKey *key = FSTTestDocKey(path);
+FSTDeletedDocument *FSTTestDeletedDoc(const absl::string_view path,
+                                      FSTTestSnapshotVersion version) {
+  DocumentKey key = testutil::Key(path);
   return [FSTDeletedDocument documentWithKey:key version:FSTTestVersion(version)];
 }