Horizon: error messages are not clear when creating strategy

[Enzo Candotti]

Brief Description
-----------------
Error messages are not clear enough when something goes wrong at the moment of creating the strategy. For example, creating a strategy for an nonexistent subcloud or subcloud group. The same error message is displayed: "Error: Strategy creation failed."

Severity
-----------------
 Minor

Steps to Reproduce
-----------------
Create a strategy for an invalid subcloud.

Expected Behavior
-----------------
Display a message with more info, for example:
Error: Strategy creation failed: "Bad strategy request: Invalid subcloud name"

Actual Behavior
-----------------
A generic error message is displayed. The user may not know what has gone wrong.

Reproducibility
-----------------
100% reproducible

System Configuration
-----------------
DC system + at least one subcloud.

Test Activity
-----------------
Feature Testing

Workaround
-----------------
Check /var/log/horizon.log for more information.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/gui/+/811240

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/gui/+/811240
Committed: https://opendev.org/starlingx/gui/commit/44b6ba9a4ae21c7a0a946e2f6e29e5079b6ed249
Submitter: "Zuul (22348)"
Branch: master

commit 44b6ba9a4ae21c7a0a946e2f6e29e5079b6ed249
Author: Enzo Candotti <email address hidden>
Date: Mon Sep 27 18:57:32 2021 -0300

    Adding more info on strategy apply error message

    Error messages are not clear enough when something goes wrong at
    the moment of creating the strategy. For example, when creating
    a strategy for an nonexistent subcloud or subcloud group, the same
    error message was displayed:
    "Error: Strategy creation failed."

    This change add more information about the error. For instance:
    Error: Strategy creation failed: "Invalid group_id"

    Closes-Bug: 1944766

    Signed-off-by: Enzo Candotti <email address hidden>
    Change-Id: Ie6d368537fa826e1995ffc961bba34e8b08f7c3c