fix(microservices): handle creating error header from typical object

[JoshVee]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

When an error is thrown by a Kafka message handler, the ServerKafka will attempt to add the error message to a header named kafka_nest-err.

This logic assumes the error can be converted directly to a Buffer via Buffer.from(err). This does not support Error objects (or typical Nest RpcException).

Issue Number: N/A

What is the new behavior?

It now checks for a message property before attempting to convert the error value to a Buffer.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 31edb5fe-ec04-41b5-9acf-704e4d3dbabc

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 53 unchanged lines in 13 files lost coverage.
• Overall coverage decreased (-0.05%) to 94.08%

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Files with Coverage Reduction	New Missed Lines	%
packages/common/utils/is-uuid.ts	1	83.33%
packages/core/exceptions/exceptions-handler.ts	1	93.33%
packages/core/injector/module-token-factory.ts	1	94.29%
packages/core/router/sse-stream.ts	1	92.59%
packages/core/services/reflector.service.ts	1	89.29%
packages/common/file-stream/streamable-file.ts	2	76.19%
packages/core/helpers/messages.ts	3	77.27%
packages/core/router/route-path-factory.ts	4	90.59%
packages/microservices/server/server.ts	4	92.16%
packages/microservices/client/client-nats.ts	5	87.41%

Totals
Change from base Build 0d5c684c-d10b-41c2-9ae2-bc7e388dc612:	-0.05%
Covered Lines:	5658
Relevant Lines:	6014

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💛 - Coveralls