refactor: add explicit this-> where possible

I have knowingly skipped some files/portions of files where this would
create merge conflicts for other open PRs.

src/util/QByteArrayBuffer.hpp

@@ -36,37 +36,37 @@ struct QByteArrayBuffer {
 
         [[nodiscard]] constexpr reference operator*() const noexcept
         {
-            return *ptr;
+            return *this->ptr;
         }
 
         [[nodiscard]] constexpr pointer operator->() const noexcept
         {
-            return ptr;
+            return this->ptr;
         }
 
         constexpr ConstIterator &operator++() noexcept
         {
-            ++ptr;
+            ++this->ptr;
             return *this;
         }
 
         constexpr ConstIterator operator++(int) noexcept
         {
             ConstIterator tmp = *this;
-            ++ptr;
+            ++this->ptr;
             return tmp;
         }
 
         constexpr ConstIterator &operator--() noexcept
         {
-            --ptr;
+            --this->ptr;
             return *this;
         }
 
         constexpr ConstIterator operator--(int) noexcept
         {
             ConstIterator tmp = *this;
-            --ptr;
+            --this->ptr;
             return tmp;
         }
 

src/util/RatelimitBucket.cpp

@@ -26,17 +26,17 @@ void RatelimitBucket::send(QString channel)
 
 void RatelimitBucket::handleOne()
 {
-    if (queue_.isEmpty())
+    if (this->queue_.isEmpty())
     {
         return;
     }
 
-    auto item = queue_.takeFirst();
+    auto item = this->queue_.takeFirst();
 
     this->budget_--;
-    callback_(item);
+    this->callback_(item);
 
-    QTimer::singleShot(cooldown_, this, [this] {
+    QTimer::singleShot(this->cooldown_, this, [this] {
         this->budget_++;
         this->handleOne();
     });

src/util/XDGDesktopFile.hpp

@@ -26,7 +26,7 @@ public:
     /// isValid returns true if the file exists and is readable
     bool isValid() const
     {
-        return valid;
+        return this->valid;
     }
 
     /// Find the first desktop file based on the given desktop file ID