500 Internal Server Error when user tries to login to Domino UI after upgrade to 5.1 from 4.6

Problem/Symptom: 

User is getting 500 Internal Server Error when try to login to Domino UI, 

500 on GET request requestOfflineToken

Cause: 

• Mismatch email in mongoDB vs what was in keycloak

{
	"_id" : ObjectId("619b70a5b330268fdaf864e0"),
	"idpId" : "498ae2d9-5996-446d-a33a-5046ae336cfb",
	"loginId" : {
		"id" : "user1",
		"lowercaseId" : "user1"
	},
	"firstName" : "first",
	"lastName" : "last",
	"fullName" : "first last",
	"email" : "first.a.last@company.com",
	"created" : ISODate("2021-11-22T10:27:49.912Z"),
	"planInfo" : {
		"trialStartDate" : ISODate("2021-11-22T10:27:49.912Z"),
		"freeRunsForAllProjects" : false
	},
	"_systemRoles" : [
		"Practitioner"
	],
	"sshKeys" : [ ],
	"gitDomainCredentials" : [ ],
	"deactivatedFlag" : false,
	"productOptIn" : true,
	"marketingOptIn" : false,
	"isDominoEmployee" : false,
	"hashedApiKey" : "02771e03e79411ab8034dad1f94c0a8bbfb6609b"
}

In keycloak for above user id, the email is "first.a.last@company_ext.com"

• Some of users such as contractors may have multiple email addresses, like xxxx@company.com and xxxx@company_ext.com, and hence mismatch between what is in keycloak and what is in mongo, give us encrypted messages about offline token

Solution: 

Perform MongoDB surgery to update the user email address to match what's in keycloak, please contact BMS Domino admin to run the command to resolve the issue. 

db.users.update({"loginId.id"."user1"},{$set: {"email" : "first.a.last@company_ext.com"}})