feat: implement permissions public api

[roaminggypsy]

No description provided.

[wfa-reviewable]

This change is 

[SanjayVas]

Reviewed 3 of 7 files at r1, 4 of 4 files at r2, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @roaminggypsy)

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src/main/kotlin/org/wfanet/measurement/access/service/v1alpha/PermissionsService.kt line 112 at r2 (raw file):

    val internalResponse: InternalListPermissionsResponse =
      internalPermissionStub.listPermissions(

Handle StatusException

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src/main/kotlin/org/wfanet/measurement/access/service/v1alpha/PermissionsService.kt line 158 at r2 (raw file):

        internalPermissionStub.checkPermissions(
          internalCheckPermissionsRequest {
            if (request.protectedResource.isNotEmpty()) {

nit: you don't technically need this check, as setting this field to its default value of empty string is equivalent to not setting it

[roaminggypsy]

Reviewable status: 6 of 7 files reviewed, 1 unresolved discussion (waiting on @SanjayVas)

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src/main/kotlin/org/wfanet/measurement/access/service/v1alpha/PermissionsService.kt line 112 at r2 (raw file):

Previously, SanjayVas (Sanjay Vasandani) wrote…

Handle StatusException

Done.

[SanjayVas]

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @roaminggypsy)

[stevenwarejones]

Reviewed 3 of 7 files at r1, 3 of 4 files at r2, 1 of 1 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @roaminggypsy)