Calendar: Usernames containing whitespace prevent being invitied to event

[dertorsten]

Steps to reproduce

1. • Create User with username containing whitespace, e.g. "John Doe" with valid mail address
   • Create User with username not containing whitespace, e.g. "John_Doe"
2. Open Calendar App, create new event.
   You may save the event or add attendees to the event.
3. Save the event
   When a user containing whitespace in his username is added to the event the save operation never finishes.

Expected behaviour

Event should be saved, users should be invited.

Actual behaviour

Event is not saved, progress circles spin forever

Server configuration

Operating system:
Ubuntu 18.04

Web server:
Nginx

Database:
Mysql

PHP version:
7.3 FPM

Nextcloud version: (see Nextcloud admin page)
19.0.2.2 - but also tested with 18.0.8

Updated from an older Nextcloud/ownCloud or fresh install:
Updated from 18

Where did you install Nextcloud from:
Official package

Signing status:

Signing status

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

List of activated apps:

- accessibility: 1.5.0 - activity: 2.12.0 - admin_audit: 1.9.0 - appointments: 1.7.2 - bbb: 1.0.2 - calendar: 2.0.4 - cloud_federation_api: 1.2.0 - comments: 1.9.0 - contacts: 3.3.0 - contactsinteraction: 1.0.0 - dav: 1.15.0 - deck: 1.0.5 - federatedfilesharing: 1.9.0 - federation: 1.9.0 - files: 1.14.0 - files_antivirus: 3.0.0 - files_external: 1.10.0 - files_pdfviewer: 1.8.0 - files_rightclick: 0.16.0 - files_sharing: 1.11.0 - files_trashbin: 1.9.0 - files_versions: 1.12.0 - files_videoplayer: 1.8.0 - forms: 2.0.4 - logreader: 2.4.0 - lookup_server_connector: 1.7.0 - nextcloud_announcements: 1.8.0 - notifications: 2.7.0 - oauth2: 1.7.0 - onlyoffice: 5.0.0 - password_policy: 1.9.1 - photos: 1.1.0 - polls: 1.4.3 - privacy: 1.3.0 - provisioning_api: 1.9.0 - recommendations: 0.7.0 - serverinfo: 1.9.0 - settings: 1.1.0 - sharebymail: 1.9.0 - spreed: 9.0.3 - support: 1.2.1 - systemtags: 1.9.0 - text: 3.0.1 - theming: 1.10.0 - twofactor_backupcodes: 1.8.0 - updatenotification: 1.9.0 - viewer: 1.3.0 - workflowengine: 2.1.0 Disabled: - encryption - firstrunwizard - survey_client - user_ldap

Nextcloud configuration:

Config report

{
    "system": {
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "localhost",
            "host.domain"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "19.0.2.2",
        "overwrite.cli.url": "https:\/\/host.domain",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": "0",
            "timeout": "0.0"
        },
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "filelocking.enabled": "true",
        "enable_previews": "true",
        "enabledPreviewProviders": [
            "OC\\Preview\\PNG",
            "OC\\Preview\\JPEG",
            "OC\\Preview\\GIF",
            "OC\\Preview\\BMP",
            "OC\\Preview\\XBitmap",
            "OC\\Preview\\Movie",
            "OC\\Preview\\PDF",
            "OC\\Preview\\MP3",
            "OC\\Preview\\TXT",
            "OC\\Preview\\MarkDown"
        ],
        "preview_max_x": "1024",
        "preview_max_y": "768",
        "preview_max_scale_factor": "1",
        "auth.bruteforce.protection.enabled": "true",
        "trashbin_retention_obligation": "auto,7",
        "skeletondirectory": "",
        "defaultapp": "file",
        "activity_expire_days": "14",
        "integrity.check.disabled": "false",
        "updater.release.channel": "stable",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_sendmailmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "maintenance": false,
        "loglevel": 2,
        "theme": "",
        "mail_smtpauthtype": "PLAIN",
        "mail_smtpsecure": "tls",
        "mail_smtpauth": 1,
        "mail_smtpport": "25",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***"
    }
}

Are you using external storage, if yes which one: local/smb/sftp/...
no

Are you using encryption:
no

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...
no

### Client configuration
**Browser:**
FF 80 / current Chrome

**Operating system:**
Linux / Mac / Windows

### Logs


</details>

[skjnldsv]

Fixed by #22770