Add. database class

```Lua
local Database = require "resources.functions.database"
local dbh = Database.new('system')

--get the domain_uuid
if (domain_uuid == nil) and (domain_name ~= nil) then
  local sql = "SELECT domain_uuid FROM v_domains "
  sql = sql .. "WHERE domain_name='" .. domain_name .. "';"
  domain_uuid = dbh:first_value(sql)
end

local dbh_switch = Database.new('switch') -- check also SQLite file.

local row = dbh_switch:first_row(sql)
if row then
  ...
end
```

resources/install/scripts/resources/functions/database.lua

@@ -0,0 +1,107 @@
+require 'resources.config'
+require 'resources.functions.database_handle'
+
+local unpack = unpack or table.unpack
+
+local Database = {} do
+
+Database.__index = Database
+
+function Database.new(name)
+	local dbh = assert(name)
+	if type(name) == 'string' then
+		if name == 'switch' and file_exists(database_dir.."/core.db") then
+			dbh = freeswitch.Dbh("sqlite://"..database_dir.."/core.db")
+		else
+			dbh = database_handle(name)
+		end
+	end
+	assert(dbh:connected())
+
+	local self = setmetatable({
+		_dbh = dbh;
+	}, Database)
+
+	return self
+end
+
+function Database:query(sql, fn)
+	return self._dbh:query(sql, fn)
+end
+
+function Database:first_row(sql)
+	local result
+	local ok, err = self:query(sql, function(row)
+		result = row
+		return 1
+	end)
+	if not ok then return nil, err end
+	return result
+end
+
+function Database:first_value(sql)
+	local result, err = self:first_row(sql)
+	if not result then return nil, err end
+	local k, v = next(result)
+	return v
+end
+
+function Database:first(sql, ...)
+	local result, err = self:first_row(sql)
+	if not result then return nil, err end
+	local t, n = {}, select('#', ...)
+	for i = 1, n do
+		t[i] = result[(select(i, ...))]
+	end
+	return unpack(t, 1, n)
+end
+
+function Database:fetch_all(sql)
+	local result = {}
+	local ok, err = self:query(sql, function(row)
+		result[#result + 1] = row
+	end)
+	if not ok then return nil, err end
+	return result
+end
+
+function Database:release(sql)
+	if self._dbh then
+		self._dbh:release()
+		self._dbh = nil
+	end
+end
+
+function Database:connected(sql)
+	return self._dbh and self._dbh:connected()
+end
+
+function Database.__self_test__()
+	local db = Database.new('system')
+	assert(db:connected())
+
+	assert("1" == db:first_value("select 1 as v"))
+
+	local t = assert(db:first_row("select 1 as v"))
+	assert(t.v == "1")
+
+	t = assert(db:fetch_all("select 1 as v union all select 2 as v"))
+	assert(#t == 2)
+	assert(t[1].v == "1")
+	assert(t[2].v == "2")
+
+	local a, b = assert(db:first("select 1 as b, 2 as a", 'a', 'b'))
+	assert(a == "2")
+	assert(b == "1")
+
+	-- assert(nil == db:first_value("some non sql query"))
+
+	db:release()
+	assert(not db:connected())
+end
+
+end
+
+-- Database.__self_test__()
+
+return Database