chore: improvements to keycloak local development (#26518)

* update keycloak docker image

* update realm file with a compatible realm

* import realm on start-docker command

Since bitnami's image does not support importing directly, the import of the test realm is done in the make file start-docker action

* Use official image from quay

* updated realm keycloak config

* final note about nickname attrib for saml

* add admin user

* update realm

* Updated from master

* Updated docs

* local typo

* use jq for ldap and saml

* updated readme

server/build/docker/keycloak/saml.mmsettings.json

@@ -0,0 +1,38 @@
+{
+    "SamlSettings": {
+        "Enable": true,
+        "EnableSyncWithLdap": false,
+        "EnableSyncWithLdapIncludeAuth": false,
+        "IgnoreGuestsLdapSync": false,
+        "Verify": false,
+        "Encrypt": false,
+        "SignRequest": false,
+        "IdpURL": "http://localhost:8484/realms/mattermost/protocol/saml",
+        "IdpDescriptorURL": "http://localhost:8484/realms/mattermost",
+        "IdpMetadataURL": "http://localhost:8484/realms/mattermost/protocol/saml/descriptor",
+        "ServiceProviderIdentifier": "mattermost",
+        "AssertionConsumerServiceURL": "http://localhost:8065/login/sso/saml",
+        "SignatureAlgorithm": "RSAwithSHA1",
+        "CanonicalAlgorithm": "Canonical1.0",
+        "ScopingIDPProviderId": "",
+        "ScopingIDPName": "",
+        "IdpCertificateFile": "saml-idp.crt",
+        "PublicCertificateFile": "",
+        "PrivateKeyFile": "",
+        "IdAttribute": "uid",
+        "GuestAttribute": "",
+        "EnableAdminAttribute": false,
+        "AdminAttribute": "",
+        "FirstNameAttribute": "givenName",
+        "LastNameAttribute": "surname",
+        "EmailAttribute": "mail",
+        "UsernameAttribute": "uid",
+        "NicknameAttribute": "cn",
+        "LocaleAttribute": "",
+        "PositionAttribute": "title",
+        "LoginButtonText": "SAML",
+        "LoginButtonColor": "#34a28b",
+        "LoginButtonBorderColor": "#2389D7",
+        "LoginButtonTextColor": "#ffffff"
+    }
+}