create fully functional get method

com/Unit/Get.lua

@@ -0,0 +1,54 @@
+-- File com/Unit/Get.lua
+--
+-- Created at 2025-09-25 20:04
+--
+-- Updated at - 
+
+local log = require("internal.log")
+local db = require("internal.database.sqlite").connect("db/unit.db", {log = true})
+local session = require("internal.session")
+
+local common = require("com/Unit/_common")
+
+-- Preparing for first db query
+local function close_db()
+  if db then
+    log.debug("Closing DB connection")
+    db:close()
+    db = nil
+  end
+end
+
+local params = session.request.params.get()
+
+local ok, mp = common.CheckMissingElement({"by", "value"}, params)
+if not ok then
+  close_db()
+  session.response.send_error(-32602, "Missing params", mp)
+end
+
+if not (params.by == "email" or params.by == "username" or params.by == "user_id") then
+  close_db()
+  session.response.send_error(-32602, "Invalid 'by' param")
+end
+
+local unit, err = db:query_row(
+  "SELECT user_id, username, email, created_at, updated_at, deleted_at, entry_status FROM units WHERE "..params.by.." = ? AND deleted_at IS NULL LIMIT 1",
+  {
+    params.value
+  }
+)
+
+if err then
+  close_db()
+  log.error("DB query error: " .. tostring(err))
+  session.response.send_error("Database query failed")
+end
+
+if not unit then
+  close_db()
+  session.response.send_error(-32102, "Unit is not exists")
+end
+
+close_db()
+session.response.send(unit)