FindGuid helper function (#3762)

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## Summary of the Pull Request
Adds a simple helper function to look up the GUID associated with a profile name.

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## References

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## PR Checklist
* [x] Closes #3680
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [x] Tests added/passed. Yes, new test group in `SettingsTests`!
* [ ] Requires documentation to be updated
* [x] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #3680

<!-- Provide a more detailed description of the PR, other things fixed or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
Very simple function, for-each through profiles checking for a match. Returns the associated GUID if found, else returns the null GUID.

This function is marked as `noexcept` to comply with assumption made by other `CascadiaSettings` functions that [`Profiles::GetGuid`](https://github.com/microsoft/terminal/blob/master/src/cascadia/TerminalApp/Profile.cpp#L141) does not throw, despite it throwing.

<!-- Describe how you validated the behavior. Add automated tests wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
The new function is simple and can be visually validated, but added tests regardless. A new test group was added in `SettingsTests` called `TestHelperFunctions` to validate the new function `FindGuid` and older function `FindProfile`. This test group could be used to validate more helper functions in `CascadiaSettings` as they're added. The new test group passes after running `te.exe TerminalApp.LocalTests.dll`. 


--------------------------------------------

* Added FindGuid helper function

* Style change

* Tests for FindGuid and FindProfile

* Fixed code format?

* Code format guess

No feedback from the Azure pipeline

* optional<GUID> fix

* Updated function desc

src/cascadia/LocalTests_TerminalApp/SettingsTests.cpp

@@ -49,6 +49,7 @@ namespace TerminalAppLocalTests
         TEST_METHOD(TestExplodingNameOnlyProfiles);
         TEST_METHOD(TestHideAllProfiles);
         TEST_METHOD(TestInvalidColorSchemeName);
+        TEST_METHOD(TestHelperFunctions);
 
         TEST_METHOD(TestLayerGlobalsOnRoot);
 
@@ -1264,6 +1265,67 @@ namespace TerminalAppLocalTests
         VERIFY_ARE_EQUAL(L"Campbell", settings._profiles.at(2)._schemeName.value());
     }
 
+    void SettingsTests::TestHelperFunctions()
+    {
+        const std::string settings0String{ R"(
+        {
+            "defaultProfile" : "{2C4DE342-38B7-51CF-B940-2309A097F518}",
+            "profiles": [
+                {
+                    "name" : "profile0",
+                    "guid": "{6239a42c-5555-49a3-80bd-e8fdd045185c}"
+                },
+                {
+                    "name" : "profile1",
+                    "guid": "{6239a42c-6666-49a3-80bd-e8fdd045185c}"
+                },
+                {
+                    "name" : "Ubuntu",
+                    "guid" : "{2C4DE342-38B7-51CF-B940-2309A097F518}"
+                },
+                {
+                    "name" : "ThisProfileShouldNotCrash"
+                }
+            ]
+        })" };
+
+        auto name0{ L"profile0" };
+        auto name1{ L"profile1" };
+        auto name2{ L"Ubuntu" };
+        auto badName{ L"DoesNotExist" };
+
+        auto guid0{ Microsoft::Console::Utils::GuidFromString(L"{6239a42c-5555-49a3-80bd-e8fdd045185c}") };
+        auto guid1{ Microsoft::Console::Utils::GuidFromString(L"{6239a42c-6666-49a3-80bd-e8fdd045185c}") };
+        auto guid2{ Microsoft::Console::Utils::GuidFromString(L"{2C4DE342-38B7-51CF-B940-2309A097F518}") };
+        std::optional<GUID> badGuid{};
+
+        VerifyParseSucceeded(settings0String);
+
+        CascadiaSettings settings;
+        settings._ParseJsonString(settings0String, false);
+        settings.LayerJson(settings._userSettings);
+
+        VERIFY_ARE_EQUAL(guid0, settings.FindGuid(name0));
+        VERIFY_ARE_EQUAL(guid1, settings.FindGuid(name1));
+        VERIFY_ARE_EQUAL(guid2, settings.FindGuid(name2));
+        VERIFY_ARE_EQUAL(badGuid, settings.FindGuid(badName));
+        // Following test will fail because GetGuid throws (despite being noexcept)
+        // VERIFY_ARE_EQUAL(badGuid, settings.FindGuid(L"ThisProfileShouldNotCrash"));
+
+        // Following lines only work because the GUID-less profile is last
+        auto prof0{ settings.FindProfile(guid0) };
+        auto prof1{ settings.FindProfile(guid1) };
+        auto prof2{ settings.FindProfile(guid2) };
+        // Following line will fail because GetGuid throws (despite being noexcept)
+        // auto badProf{ settings.FindProfile(badGuid) };
+
+        VERIFY_ARE_EQUAL(name0, prof0->GetName());
+        VERIFY_ARE_EQUAL(name1, prof1->GetName());
+        VERIFY_ARE_EQUAL(name2, prof2->GetName());
+        // Following test will fail because GetGuid throws (despite being noexcept)
+        // VERIFY_ARE_EQUAL(badName, badProf->GetName());
+    }
+
     void SettingsTests::TestLayerGlobalsOnRoot()
     {
         // Test for microsoft/terminal#2906. We added the ability for the root

src/cascadia/TerminalApp/CascadiaSettings.cpp

@@ -63,6 +63,29 @@ CascadiaSettings::CascadiaSettings(const bool addDynamicProfiles)
     }
 }
 
+// Method Description:
+// - Finds a GUID associated with the given profile name. If no profile matches
+//      the profile name, returns a std::nullopt.
+// Arguments:
+// - profileName: the name of the profile's GUID to return.
+// Return Value:
+// - the GUID associated with the profile name.
+std::optional<GUID> CascadiaSettings::FindGuid(const std::wstring& profileName) const noexcept
+{
+    std::optional<GUID> profileGuid{};
+
+    for (const auto& profile : _profiles)
+    {
+        if (profileName == profile.GetName())
+        {
+            profileGuid = profile.GetGuid();
+            break;
+        }
+    }
+
+    return profileGuid;
+}
+
 // Method Description:
 // - Finds a profile that matches the given GUID. If there is no profile in this
 //      settings object that matches, returns nullptr.

src/cascadia/TerminalApp/CascadiaSettings.h

@@ -65,6 +65,7 @@ public:
     static std::wstring GetSettingsPath(const bool useRoamingPath = false);
     static std::wstring GetDefaultSettingsPath();
 
+    std::optional<GUID> FindGuid(const std::wstring& profileName) const noexcept;
     const Profile* FindProfile(GUID profileGuid) const noexcept;
 
     std::vector<TerminalApp::SettingsLoadWarnings>& GetWarnings();