Feature/bump to terraform sdk 2.0 rebase

[dikhan]

What problem does this Pull Request solve?

Please link to the issue number here (issue will be closed when PR is merged): Closes #268

Terraform Plugin SDK v2 Upgrade checklist:

• [x] Dropped Support for Terraform 0.11 and Below
• [x] Version 2 of the Module
• [x] A New Acceptance Testing Driver
• [x] More Support for context.Context
• [x] Support for Diagnostics
• [x] Support for Resource-Level and Field-Level Descriptions
• [ ] New Diagnostics-Enabled Map Validators
• [ ] Support for Debuggable Provider Binaries
• [ ] Support for Provider Metadata
• [ ] Louder helper/schema.ResourceData.Set Errors in Testing
• [ ] More Consistent Usage of github.com/mitchellh/go-testing-interface
• [ ] Corrected Results of helper/acctest.RandIntRange
• [ ] Clearer Handling of nil for helper/resource.NonRetryableError and helper/resource.RetryableError
• [ ] More Robust Handling of helper/schema.TypeSet Hashes
• [ ] Stronger Validation for helper/schema.Schema.Computed Fields
• [x] More Robust Validation of helper/schema.TypeMap Elems
• [ ] More Robust Validation of helper/resource.TestCheckResourceAttrPair
• [ ] More Robust Validation of Test Sweepers
• [ ] Deprecation of helper/schema.ExistsFunc
• [x] Deprecation of helper/schema.SchemaValidateFunc
• [ ] Removal of helper/mutexkv Package
• [ ] Removal of helper/pathorcontents Package
• [ ] Removal of httpclient Package
• [ ] Removal of helper/hashcode Package
• [ ] Removal of the acctest Package
• [ ] Removal of the terraform.ResourceProvider Interface
• [ ] Removal of the helper/schema.Provider.StopContext method
• [ ] Removal of helper/schema.ResourceData.SetPartial
• [ ] Removal of the helper/schema.Provider.MetaReset property
• [ ] Removal of Deprecated Validation Functions
• [ ] Removal of helper/schema.Schema.PromoteSingle
• [ ] Removal of helper/schema.ResourceData.UnsafeSetFieldRaw
• [ ] Removal of helper/schema.Resource.Refresh
• [ ] Removal of helper/schema.Schema.Removed
• [ ] Removal of helper/encryption Package
• [ ] Removal of Discouraged Variables, Functions, Types, and Interfaces

Type of change

What type of change does your code introduce to the provider? Please put an x (w/o heading/trailing white spaces) in the boxes that apply:

• [x] New feature (change that adds new functionality)
• [ ] Bug-fix (change that fixes current functionality)
• [ ] Tech debt (enhances the current functionality)
• [ ] New release (pumps the version)

Checklist

Please put an x (w/o heading/trailing white spaces) in the boxes that apply:

• [x] I have read and followed the CONTRIBUTING guidelines
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have made sure code compiles correctly and all tests are passing by running make test-all
• [x] I have added/updated necessary documentation (if appropriate)
• [x] I have added the following info to the title of the PR (pick the appropriate option for the type of change). This is important because the release notes will include this information.
  • [x] Feature Request: PRs related to feature requests should have in the title [FeatureRequest: Issue #X] <PR Title>
  • [ ] Bug Fixes: PRs related to bug fixes should have in the title [BugFix: Issue #X] <PR Title>
  • [ ] Tech Debt: PRs related to technical debt should have in the title [TechDebt: Issue #X] <PR Title>
  • [ ] New Release: PRs related to a new release should have in the title [NewRelease] vX.Y.Z

Checklist for Admins

• [x] Label is populated
• [x] PR is assigned to the corresponding project
• [x] PR has at least 1 reviewer and 1 assignee

[codecov[bot]]

Codecov Report

Merging #275 (3d2b872) into master (5d335a8) will increase coverage by 1.08%. The diff coverage is 85.41%.

@@            Coverage Diff             @@
##           master     #275      +/-   ##
==========================================
+ Coverage   90.97%   92.05%   +1.08%     
==========================================
  Files          61       60       -1     
  Lines        3091     3021      -70     
==========================================
- Hits         2812     2781      -31     
+ Misses        184      155      -29     
+ Partials       95       85      -10     

Impacted Files	Coverage Δ
openapi/data_source_factory.go	97.97% <ø> (ø)
openapi/data_source_instance_factory.go	100.00% <ø> (ø)
openapi/openapi_client.go	84.54% <ø> (ø)
openapi/openapi_spec_header.go	100.00% <ø> (ø)
openapi/openapi_spec_resource_schema_definition.go	97.36% <ø> (ø)
.../openapi_spec_security_definition_apikey_header.go	100.00% <ø> (ø)
...i_spec_security_definition_apikey_header_bearer.go	100.00% <ø> (ø)
...i/openapi_spec_security_definition_apikey_query.go	100.00% <ø> (ø)
...pi_spec_security_definition_apikey_query_bearer.go	100.00% <ø> (ø)
...i_spec_security_definition_apikey_refresh_token.go	84.21% <ø> (ø)
... and 23 more

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Continue to review full report at Codecov.

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[dikhan]

PR created as an attempt to trigger again travis and get build confirmation...Closing in favour of duplicated PR: https://github.com/dikhan/terraform-provider-openapi/pull/274