fix(saml): Push AuthenticationSucceededOnApplication milestone for SAML sessions (#10263)

# Which Problems Are Solved

The SAML session (v2 login) currently does not push a
`AuthenticationSucceededOnApplication` milestone upon successful SAML
login for the first time. The changes in this PR address this issue.

# How the Problems Are Solved

Add a new function to set the appropriate milestone, and call this
function after a successful SAML request.

# Additional Changes

N/A

# Additional Context

- Closes #9592

---------

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>

internal/command/saml_session_test.go

@@ -334,6 +334,7 @@ func TestCommands_CreateSAMLSessionFromSAMLRequest(t *testing.T) {
 				idGenerator:  tt.fields.idGenerator,
 				keyAlgorithm: tt.fields.keyAlgorithm,
 			}
+			c.setMilestonesCompletedForTest("instanceID")
 			err := c.CreateSAMLSessionFromSAMLRequest(tt.args.ctx, tt.args.samlRequestID, tt.args.complianceCheck, tt.args.samlResponseID, tt.args.samlResponseLifetime)
 			require.ErrorIs(t, err, tt.res.err)
 		})