[FIX] fleet: always include current month in costs report

When consulting the costs reports, if the beginning of the dates range
has a day greater than the day of today (e.g., start date: 2021/02/25,
today: 2021/07/10 => 25 > 10), the costs of the current month won't be
include in the report.

To reproduce the issue:
(DB without any demo data. Let X be the day of the month for today)
1. Create a vehicle V
2. Add a service S1 for V
    - The category of the service type does not matter
    - Cost: 500
    - Date: today
3. Add a second service S2 for V
    - Same service type
    - Cost: 250
    - Date: Last month with a day > X (so if today is 2021/07/26, date
could be 2021/06/27)
4. Fleet > Reporting > Costs

Error: The report does not include S1

When generating the dates range, the current date is used as the end of
the interval. Since the interval step is '1 month', it will lead to an
issue in the above case:
Suppose today is 2021/07/26, the interval starts on 2021/06/27. Then, if
we add one month to this date, we have 2021/07/27, which is after the
end of the interval (2021/07/26), so the date is ignored. As a result,
current month won't be included in the report.

Note: A similar issue can happen with the contracts

OPW-2477004

closes #74219

Signed-off-by: Kevin Baptiste <kba@odoo.com>

addons/fleet/report/fleet_report.py

@@ -43,7 +43,7 @@ def init(self):
     CROSS JOIN generate_series((
             SELECT
                 min(date)
-                FROM fleet_vehicle_log_services), CURRENT_DATE, '1 month') d
+                FROM fleet_vehicle_log_services), CURRENT_DATE + '1 month'::interval, '1 month') d
         LEFT JOIN fleet_vehicle_log_services se ON se.vehicle_id = ve.id
             AND date_trunc('month', se.date) = date_trunc('month', d)
     WHERE
@@ -74,7 +74,7 @@ def init(self):
     CROSS JOIN generate_series((
             SELECT
                 min(acquisition_date)
-                FROM fleet_vehicle), CURRENT_DATE, '1 month') d
+                FROM fleet_vehicle), CURRENT_DATE + '1 month'::interval, '1 month') d
         LEFT JOIN fleet_vehicle_log_contract co ON co.vehicle_id = ve.id
             AND date_trunc('month', co.date) = date_trunc('month', d)
         LEFT JOIN fleet_vehicle_log_contract cod ON cod.vehicle_id = ve.id