Add import for index mappings

[rblcoder]

Description

Implement import of index mappings

Issues Resolved

#135 #71

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[rblcoder]

Hi @prudhvigodithi , please review this PR.

[prudhvigodithi]

Hey @rblcoder thanks for your contribution, one question I have is since this logic is added to the resourceOpensearchIndexRead function is behaviour to 1st read the existing mapping and continue them with next terraform apply operations ? When I import the mappings which will be stored in StateContext with this code change in resourceOpensearchIndexRead does it read the imported mappings and continue with terraform apply operation?

Thank you

[rblcoder]

@prudhvigodithi The read function is now able to read the mappings attribute from the underlying infrastructure.
I have tested by removing the resource from state. Then imported it using the import command. The state file is getting updated successfully with the mappings information. Post this, I am able to run and continue with apply.

[prudhvigodithi]

Thanks @rblcoder, LGTM.
@bbarani @peterzhuamazon @phillbaker

[xsnrg]

@rblcoder Thank you. @prudhvigodithi any chance of getting a new release created with this fix?