Add implementation for exposing all BPN groups.

[bmg13]

WHAT

Adds a new /groups endpoint to resolve all BPN Groups. Implementation of this Decision Record.

WHY

To ease the listing of all BPN groups stored.

FURTHER NOTES

As defined in the DR, this endpoint is added in the BusinessPartnerGroupApiV3.

Request:
GET /v3/business-partner-groups/groups

Example response:

{
	"tx:groups": [
		"group2",
		"group4",
		"group13",
		"group10",
		"group3",
		"group1",
		"group5"
	],
	"@context": {...}
}

Closes #1898

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud