Consul - Add support for metadata in a backwards compatible way

[cieciurm]

Description

This PR backports #1167 to 3.x

I'd like to open a discussion on some details regarding implementation before completing it and adding tests.

I tried to get some inspiration from Spring Cloud Consul implementation:

• Added TagsAsMetadata (defaults to true)
• This setting controls whether we fallback to Metadata creation from Tags (default) or we use the real Metadata
• Both approaches add default metadata

Let me know if this is what you had in mind. I will add unit tests then.
Documentation changes will follow.

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[cieciurm]

Tests added, ready for review 👨🏽‍🔬.

cc @hananiel

[hananiel]

Works as expected. LGTM.

[TimHess]

/azp run Steeltoe.All

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

85.7% Coverage
0.0% Duplication

[cieciurm]

Thanks @hananiel!

I will update docs in 2 weeks time, when I'm back from my vacation.