Add Service Endpoint for Custom Services

[kur4mot0]

All Submissions:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My code follows the code style of this project.
• I ran lint checks locally prior to submission.
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What about the current behavior has changed?

Issue Number:

Does this introduce a change to go.mod, go.sum or vendor/?

• Yes
• No

Does this introduce a breaking change?

• Yes
• No

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Other information

[ghost]

All CLA requirements met.

[xuzhang3]

@kur4mot0 unit test fail

--- FAIL: TestProvider_HasChildResources (0.00s)
    provider_test.go:77: 
        	Error Trace:	provider_test.go:77
        	Error:      	Not equal: 
        	            	expected: 62
        	            	actual  : 63
        	Test:       	TestProvider_HasChildResources
        	Messages:   	There are an unexpected number of registered resources
FAIL