refactor: move url creation for mods to modplatform/

Moves all things related to creating the URLs of the mod platforms
that go to network tasks to a single place, so that:

1. Maintaining and fixing eventual issues is more straightforward.
2. Makes it possible to factor out more common code between the
   different modplatform pages

launcher/modplatform/ModAPI.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <QString>
+
+class ModAPI {
+    public:
+        virtual ~ModAPI() = default;
+
+        inline virtual QString getModSearchURL(int, QString, QString, bool, QString) const { return ""; };
+        inline virtual QString getVersionsURL(const QString& addonId) const { return ""; };
+        inline virtual QString getAuthorURL(const QString& name) const { return ""; };
+};

launcher/modplatform/flame/FlameAPI.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include "modplatform/ModAPI.h"
+
+class FlameAPI : public ModAPI {
+   public:
+    inline QString getModSearchURL(int index, QString searchFilter, QString sort, bool fabricCompatible, QString version) const override 
+    {
+        return QString("https://addons-ecs.forgesvc.net/api/v2/addon/search?"
+            "gameId=432&" "categoryId=0&" "sectionId=6&"
+
+            "index=%1&"  "pageSize=25&"       "searchFilter=%2&"
+            "sort=%3&"   "modLoaderType=%4&"  "gameVersion=%5")
+                .arg(index)
+                .arg(searchFilter)
+                .arg(sort)
+                .arg(fabricCompatible ? 4 : 1)  // Enum: https://docs.curseforge.com/?http#tocS_ModLoaderType
+                .arg(version);
+    };
+
+    inline QString getVersionsURL(const QString& addonId) const override
+    {
+        return QString("https://addons-ecs.forgesvc.net/api/v2/addon/%1/files").arg(addonId);
+    };
+
+    inline QString getAuthorURL(const QString& name) const override { return ""; };
+};

launcher/modplatform/modrinth/ModrinthAPI.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include "modplatform/ModAPI.h"
+
+class ModrinthAPI : public ModAPI {
+   public:
+    inline QString getModSearchURL(int offset, QString query, QString sort, bool fabricCompatible, QString version) const override 
+    { 
+        return QString("https://api.modrinth.com/v2/search?"
+                "offset=%1&"   "limit=25&"   "query=%2&"   "index=%3&"
+                "facets=[[\"categories:%4\"],[\"versions:%5\"],[\"project_type:mod\"]]")
+                  .arg(offset)
+                  .arg(query)
+                  .arg(sort)
+                  .arg(fabricCompatible ? "fabric" : "forge")
+                  .arg(version);
+    };
+
+    inline QString getVersionsURL(const QString& addonId) const override
+    {
+        return QString("https://api.modrinth.com/v2/project/%1/version").arg(addonId);
+    };
+
+    inline QString getAuthorURL(const QString& name) const override { return "https://modrinth.com/user/" + name; };
+};

launcher/modplatform/modrinth/ModrinthPackIndex.cpp

@@ -1,10 +1,13 @@
 #include "ModrinthPackIndex.h"
+#include "ModrinthAPI.h"
 
 #include "Json.h"
 #include "minecraft/MinecraftInstance.h"
 #include "minecraft/PackProfile.h"
 #include "net/NetJob.h"
 
+static ModrinthAPI api;
+
 void Modrinth::loadIndexedPack(ModPlatform::IndexedPack& pack, QJsonObject& obj)
 {
     pack.addonId = Json::requireString(obj, "project_id");
@@ -17,7 +20,7 @@ void Modrinth::loadIndexedPack(ModPlatform::IndexedPack& pack, QJsonObject& obj)
 
     ModPlatform::ModpackAuthor modAuthor;
     modAuthor.name = Json::requireString(obj, "author");
-    modAuthor.url = "https://modrinth.com/user/" + modAuthor.name;
+    modAuthor.url = api.getAuthorURL(modAuthor.name);
     pack.authors.append(modAuthor);
 }