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, 11 insertions, 11 deletions

diff --git a/Firestore/Example/Tests/Core/FSTViewSnapshotTest.mm b/Firestore/Example/Tests/Core/FSTViewSnapshotTest.mm
index c503684..ca8954e 100644
--- a/Firestore/Example/Tests/Core/FSTViewSnapshotTest.mm
+++ b/Firestore/Example/Tests/Core/FSTViewSnapshotTest.mm
@@ -32,7 +32,7 @@ NS_ASSUME_NONNULL_BEGIN
 @implementation FSTViewSnapshotTests
 
 - (void)testDocumentChangeConstructor {
-  FSTDocument *doc = FSTTestDoc(@"a/b", 0, @{}, NO);
+  FSTDocument *doc = FSTTestDoc("a/b", 0, @{}, NO);
   FSTDocumentViewChangeType type = FSTDocumentViewChangeTypeModified;
   FSTDocumentViewChange *change = [FSTDocumentViewChange changeWithDocument:doc type:type];
   XCTAssertEqual(change.document, doc);
@@ -42,15 +42,15 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)testTrack {
   FSTDocumentViewChangeSet *set = [FSTDocumentViewChangeSet changeSet];
 
-  FSTDocument *docAdded = FSTTestDoc(@"a/1", 0, @{}, NO);
-  FSTDocument *docRemoved = FSTTestDoc(@"a/2", 0, @{}, NO);
-  FSTDocument *docModified = FSTTestDoc(@"a/3", 0, @{}, NO);
+  FSTDocument *docAdded = FSTTestDoc("a/1", 0, @{}, NO);
+  FSTDocument *docRemoved = FSTTestDoc("a/2", 0, @{}, NO);
+  FSTDocument *docModified = FSTTestDoc("a/3", 0, @{}, NO);
 
-  FSTDocument *docAddedThenModified = FSTTestDoc(@"b/1", 0, @{}, NO);
-  FSTDocument *docAddedThenRemoved = FSTTestDoc(@"b/2", 0, @{}, NO);
-  FSTDocument *docRemovedThenAdded = FSTTestDoc(@"b/3", 0, @{}, NO);
-  FSTDocument *docModifiedThenRemoved = FSTTestDoc(@"b/4", 0, @{}, NO);
-  FSTDocument *docModifiedThenModified = FSTTestDoc(@"b/5", 0, @{}, NO);
+  FSTDocument *docAddedThenModified = FSTTestDoc("b/1", 0, @{}, NO);
+  FSTDocument *docAddedThenRemoved = FSTTestDoc("b/2", 0, @{}, NO);
+  FSTDocument *docRemovedThenAdded = FSTTestDoc("b/3", 0, @{}, NO);
+  FSTDocument *docModifiedThenRemoved = FSTTestDoc("b/4", 0, @{}, NO);
+  FSTDocument *docModifiedThenModified = FSTTestDoc("b/5", 0, @{}, NO);
 
   [set addChange:[FSTDocumentViewChange changeWithDocument:docAdded
                                                       type:FSTDocumentViewChangeTypeAdded]];
@@ -109,9 +109,9 @@ NS_ASSUME_NONNULL_BEGIN
   FSTQuery *query = FSTTestQuery("a");
   FSTDocumentSet *documents = [FSTDocumentSet documentSetWithComparator:FSTDocumentComparatorByKey];
   FSTDocumentSet *oldDocuments = documents;
-  documents = [documents documentSetByAddingDocument:FSTTestDoc(@"c/a", 1, @{}, NO)];
+  documents = [documents documentSetByAddingDocument:FSTTestDoc("c/a", 1, @{}, NO)];
   NSArray<FSTDocumentViewChange *> *documentChanges =
-      @[ [FSTDocumentViewChange changeWithDocument:FSTTestDoc(@"c/a", 1, @{}, NO)
+      @[ [FSTDocumentViewChange changeWithDocument:FSTTestDoc("c/a", 1, @{}, NO)
                                               type:FSTDocumentViewChangeTypeAdded] ];
 
   BOOL fromCache = YES;