[#MUI-33] Développer le composant Datepicker (#50)

| Numéro du ticket | Titre du ticket |
|------------------|-----------------|
|                  |                 |

## Description de la PR

## Modification du .env

## Check list

- [x] Pas de régression
- [x] TU/TI/TF rédigée
- [x] TU/TI/TF OK
- [x] CHANGELOG modifié

Reviewed-on: #50
Co-authored-by: tristan <tristan@yuno.malio.fr>
Co-committed-by: tristan <tristan@yuno.malio.fr>

app/components/malio/date/composables/datetimeFormat.ts

@@ -0,0 +1,33 @@
+import {isValidIso} from './dateFormat'
+
+const DATETIME_RE = /^(\d{4}-\d{2}-\d{2})T(\d{2}):(\d{2}):(\d{2})$/
+
+export function isValidIsoDateTime(s: string): boolean {
+  const m = DATETIME_RE.exec(s)
+  if (!m) return false
+  const [, date, hh, mm, ss] = m
+  if (!isValidIso(date)) return false
+  const h = Number(hh)
+  const min = Number(mm)
+  const sec = Number(ss)
+  return h >= 0 && h <= 23 && min >= 0 && min <= 59 && sec >= 0 && sec <= 59
+}
+
+export function formatIsoDateTimeToDisplay(s: string | null): string {
+  if (!s || !isValidIsoDateTime(s)) return ''
+  const [date, time] = s.split('T')
+  const [y, mo, d] = date.split('-')
+  const [hh, mm] = time.split(':')
+  return `${d}/${mo}/${y} ${hh}:${mm}`
+}
+
+export function splitDateTime(s: string | null): {date: string | null; time: string} {
+  if (!s || !isValidIsoDateTime(s)) return {date: null, time: ''}
+  const [date, time] = s.split('T')
+  return {date, time: time.slice(0, 5)}
+}
+
+export function composeDateTime(date: string, time: string): string {
+  const t = time || '00:00'
+  return `${date}T${t}:00`
+}