Add or remove Folder RoleAssignments not valid error

Question

Having trouble with adding or removing Role Assignments on SharePoint document folders using REST API through Power Automate.

Process is to copy a Template folder with subfolders. Of which, 2 subfolders need unique permissions to prevent unwanted user access.

I believe BreakRoleInheritance is being broken properly prior Sent POST via Send HTTP request via SharePoint:

_api/web/GetFolderByServerRelativeUrl('Shared Documents/SHOW FOLDERS/2017 Budgets/01 January/SHOW20')/ListItemAllFields/breakroleinheritance(copyRoleAssignments=true,clearSubscopes=true)

Sample command sending DELETE via HTTP to remove a SP Group with ID of (6) from folder:

_api/web/GetFolderByServerRelativeUrl(‘Shared Documents/SHOW FOLDERS/2017 Budgets/01 January/SHOW20')/ListItemAllFields/roleassignments/getbyprincipalid(6)

Error output:

{
  "status": 400,
  "message": "The expression \"web/GetFolderByServerRelativeUrl(‘Shared Documents/SHOW FOLDERS/2017 Budgets/01 January/SHOW20')/ListItemAllFields/roleassignments/getbyprincipalid(6)\" is not valid.\r\nclientRequestId: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\r\nserviceRequestId: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx\",
  "source": "https://xxxxxxxxx.sharepoint.com/sites/FILETRANSFER/_api/web/GetFolderByServerRelativeUrl(%E2%80%98Shared%20Documents/SHOW%20FOLDERS/2017%20Budgets/01%20January/SHOW20')/ListItemAllFields/roleassignments/getbyprincipalid(6)",
  "errors": [
    "-1",
    "Microsoft.SharePoint.Client.InvalidClientQueryException"
  ]
}

Answer 1

The following worked for me.

1. Break Inheritance for the folder:

method: POST, content-type:application/json;odata=verbose

_api/web/GetFolderByServerRelativeUrl('TestLibrary/2019')/ListItemAllFields/breakroleinheritance(copyRoleAssignments=true,clearSubscopes=true)

2. Grant a SharePoint group with id=19 Contribution permission to the folder:

method: POST, content-type:application/json;odata=verbose

_api/web/GetFolderByServerRelativeUrl('TestLibrary/2019')/ListItemAllFields/roleassignments/addroleassignment(principalid=19,roledefid=1073741827)

roledefid for Permission Levels are as follows:

1073741829, Full Control

1073741827, Contribute

1073741826, Read