Add new subsite to the specified site

• command: spo web add -t|--title <title> -u|--webUrl <webUrl> -w|--webTemplate <webTemplate> -p|--parentWebUrl <parentWebUrl> -d|--description [description] -l|--locale [locale] --breakInheritance --inheritNavigation
• title: Subsite title
• webUrl: last part of the URL for the subsite to be created (eg. subsite1 and not https://contoso.sharepoint.com/subsite1)
• webTemplate: Subsite template, eg. STS#0 (Classic team site)
• parentWebUrl: URL of the parent site under which to create the subsite
• description: Subsite description, optional
• locale: Subsite locale LCID, eg. 1033 for en-US
• breakInheritance: Set to not inherit permissions from the parent site
• inheritNavigation: Set to inherit the navigation from the parent site

Create subsite using:

POST <parentWebUrl>/_api/web/webinfos/add
accept: application/json;odata=nometadata
content-type: application/json;odata=nometadata
x-requestdigest: 0x5AB7E...

{
  "parameters": {  
    "Url": "<webUrl>",
    "Title": "<title>",
    "WebTemplate": "<webTemplate>",
    "UseUniquePermissions": <breakInheritance>
    ...
  }
}

Ensure you have access token for the web specified in the parentWebUrl option.