Issue#13: ADD buy implant route

Besides the new route, problems in purchasesTable and in databank were fixed

src/db/migrations/meta/0000_snapshot.json

 {
-  "id": "15e4aa47-1bc6-462d-9d9d-8c0a45e69908",
+  "id": "0de8e822-0ca4-43f4-9002-743d449c49ce",
   "prevId": "00000000-0000-0000-0000-000000000000",
   "version": "7",
   "dialect": "postgresql",
@@ -70,8 +70,8 @@
       "checkConstraints": {},
       "isRLSEnabled": false
     },
-    "public.pursaches": {
-      "name": "pursaches",
+    "public.purchases": {
+      "name": "purchases",
       "schema": "",
       "columns": {
         "id": {
@@ -86,6 +86,12 @@
           "primaryKey": false,
           "notNull": true
         },
+        "implant_id": {
+          "name": "implant_id",
+          "type": "integer",
+          "primaryKey": false,
+          "notNull": true
+        },
         "created_at": {
           "name": "created_at",
           "type": "timestamp",
@@ -96,9 +102,9 @@
       },
       "indexes": {},
       "foreignKeys": {
-        "pursaches_user_id_users_id_fk": {
-          "name": "pursaches_user_id_users_id_fk",
-          "tableFrom": "pursaches",
+        "purchases_user_id_users_id_fk": {
+          "name": "purchases_user_id_users_id_fk",
+          "tableFrom": "purchases",
           "tableTo": "users",
           "columnsFrom": [
             "user_id"
@@ -109,12 +115,12 @@
           "onDelete": "cascade",
           "onUpdate": "no action"
         },
-        "pursaches_user_id_implants_id_fk": {
-          "name": "pursaches_user_id_implants_id_fk",
-          "tableFrom": "pursaches",
+        "purchases_implant_id_implants_id_fk": {
+          "name": "purchases_implant_id_implants_id_fk",
+          "tableFrom": "purchases",
           "tableTo": "implants",
           "columnsFrom": [
-            "user_id"
+            "implant_id"
           ],
           "columnsTo": [
             "id"
@@ -125,8 +131,8 @@
       },
       "compositePrimaryKeys": {},
       "uniqueConstraints": {
-        "pursaches_id_unique": {
-          "name": "pursaches_id_unique",
+        "purchases_id_unique": {
+          "name": "purchases_id_unique",
           "nullsNotDistinct": false,
           "columns": [
             "id"