Task: Send Instagram statistics to Mattermost

n8n workflow JSON:
{"id":"3","name":"StatsInstagram","nodes":[{"name":"Mattermost","type":"n8n-nodes-base.mattermost","position":[1030,290],"parameters":{"message":"=Bonjour ! Voici les stats de notre Instagram {{$json[\"Compte\"]}} en ce beau matin du {{$node[\"Date & Time\"].json[\"day_today\"]}} {{$node[\"Date & Time\"].json[\"data\"]}}\nLe nombre de Followers est de : {{$json[\"Followers\"]}}\nNous avons réalisé : {{$json[\"Posts\"]}} posts, \nBravo !","channelId":"xxxxxxx","attachments":[],"otherOptions":{}},"credentials":{"mattermostApi":"API"},"typeVersion":1},{"name":"Date & Time","type":"n8n-nodes-base.dateTime","position":[640,290],"parameters":{"value":"={{$json[\"date_today\"]}}","custom":true,"options":{},"toFormat":"DD-MM-YYYY"},"typeVersion":1},{"name":"Cron","type":"n8n-nodes-base.cron","position":[310,290],"parameters":{"triggerTimes":{"item":[{"hour":8}]}},"typeVersion":1},{"name":"Get the date today","type":"n8n-nodes-base.function","position":[470,290],"parameters":{"functionCode":"var date = new Date().toISOString();\nvar day = new Date().getDay();\nconst weekday = [\"Dimanche\", \"Lundi\", \"Mardi\", \"Mercredi\", \"Jeudi\", \"Vendredi\", \"Samedi\"];\n\nitems[0].json.date_today = date;\nitems[0].json.day_today = weekday[day];\n\nreturn items;\n"},"typeVersion":1},{"name":"Read data on Google Sheets","type":"n8n-nodes-base.googleSheets","position":[850,290],"parameters":{"range":"cells","options":{},"sheetId":"sheetID","authentication":"oAuth2"},"credentials":{"googleSheetsOAuth2Api":"GoogleAPI"},"typeVersion":1}],"active":false,"settings":{},"connections":{"Cron":{"main":[[{"node":"Get the date today","type":"main","index":0}]]},"Date & Time":{"main":[[{"node":"Read data on Google Sheets","type":"main","index":0}]]},"Get the date today":{"main":[[{"node":"Date & Time","type":"main","index":0}]]},"Read data on Google Sheets":{"main":[[{"node":"Mattermost","type":"main","index":0}]]}}}