Add external_url= capability to Tenant.

[martinpovolny]

Add external_url= capability to Tenant.

Relevant BZ:
https://bugzilla.redhat.com/show_bug.cgi?id=1550002

This PR extends the work done in #328 in support of changes from ManageIQ/manageiq#18849

Tested automate code for "Tenant":

$evm.log(:info, $evm.root['vmdb_object_type'])
$evm.log(:info, "tenant_id: #{$evm.root['tenant_id'].inspect}")

# t = $evm.root['tenant'] # this will give the LOGGGED IN tenant, not the target object tenant
t = $evm.vmdb($evm.root['vmdb_object_type']).find_by(:id => $evm.root['tenant_id'])
$evm.log(:info, "tenant: #{t.inspect}")
t.external_url = "https://www.redhat.com"

[martinpovolny]

@miq-bot add_label bug, ivanchuk/yes

[miq-bot]

Checked commit martinpovolny@c3663e3 with ruby 2.4.6, rubocop 0.69.0, haml-lint 0.20.0, and yamllint 1.10.0
1 file checked, 0 offenses detected
Everything looks fine. 👍

[coveralls]

Pull Request Test Coverage Report for Build 2902

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 85.153%

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Totals
Change from base Build 2893:	0.03%
Covered Lines:	4961
Relevant Lines:	5826

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💛 - Coveralls

[gmcculloug]

I verified that the models updated in ManageIQ/manageiq#18849 are all accounted for now. 👍