Move MongoDB classes into a seperate db module (#62)

* move album class into mongodb dir

* inherit AlbumMethods at DB Initialization level

* move album -> db/mongodb

* move mongodb classes into separate package

server/app/db/mongodb/artists.py

@@ -0,0 +1,38 @@
+"""
+This file contains the Artists class for interacting with artist documents in MongoDB.
+"""
+from app.db.mongodb import MongoArtists
+from bson import ObjectId
+
+
+class Artists(MongoArtists):
+    """
+    The artist class for all artist related database operations.
+    """
+
+    def insert_artist(self, artist_obj: dict) -> None:
+        """
+        Inserts an artist into the database.
+        """
+        self.collection.update_one(artist_obj, {
+            "$set": artist_obj
+        },
+                                   upsert=True).upserted_id
+
+    def get_all_artists(self) -> list:
+        """
+        Returns a list of all artists in the database.
+        """
+        return self.collection.find()
+
+    def get_artist_by_id(self, artist_id: str) -> dict:
+        """
+        Returns an artist matching the mongo Id.
+        """
+        return self.collection.find_one({"_id": ObjectId(artist_id)})
+
+    def get_artists_by_name(self, query: str):
+        """
+        Returns all the artists matching the query.
+        """
+        return self.collection.find({"name": query}).limit(20)