Add initial API interaction functions and database schema

DB/db.json

@@ -0,0 +1,45 @@
+{
+  "users": [
+    {
+      "Uid": 1,
+      "username": "admin",
+      "password": "admin123",
+      "Gid": null,
+      "SGid": 0,
+      "TGid": null
+    },
+    {
+      "Uid": 2,
+      "username": "user1",
+      "password": "user123",
+      "Gid": 1,
+      "SGid": 1,
+      "TGid": null
+    }
+  ],
+  "groups": [
+    {
+      "Gid": 1,
+      "GroupName": "Public Group"
+    }
+  ],
+  "subgroups": [
+    {
+      "SGid": 0,
+      "SubGroupName": "Admin Subgroup",
+      "Gid": null
+    },
+    {
+      "SGid": 1,
+      "SubGroupName": "User Subgroup",
+      "Gid": 1
+    }
+  ],
+  "user_groups": [
+    {
+      "Uid": 2,
+      "Gid": 1,
+      "SGid": 1
+    }
+  ]
+}

DB/schema.sql

@@ -0,0 +1,27 @@
+CREATE TABLE USER (
+    Uid INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
+    username TEXT NOT NULL,
+    password TEXT NOT NULL
+);
+
+CREATE TABLE "GROUP" (
+    Gid INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
+    GroupName TEXT NOT NULL
+);
+
+CREATE TABLE SUBGROUP (
+    SGid INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
+    SubGroupName TEXT NOT NULL,
+    Gid INTEGER NOT NULL,
+    FOREIGN KEY (Gid) REFERENCES "GROUP"(Gid)
+);
+
+CREATE TABLE USER_GROUP (
+    Uid INTEGER NOT NULL,
+    Gid INTEGER NOT NULL,
+    SGid INTEGER,
+    PRIMARY KEY (Uid, Gid),
+    FOREIGN KEY (Uid) REFERENCES USER(Uid),
+    FOREIGN KEY (Gid) REFERENCES "GROUP"(Gid),
+    FOREIGN KEY (SGid) REFERENCES SUBGROUP(SGid)
+);