initial wrapper work (#3)

Initial setup including github docs, readme, and header file.
Signed-off-by: Mikaela <[email protected]>

.github/CONTRIBUTING.md

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+# How to contribute
+
+*We are still working on improving these guidelines.*
+
+Thank you for taking the time to contribute to `hyperledger/ursa-wrapper-go`!
+
+Contributing:
+* Submit a [bug report](#bug-report)
+* Submit a [pull request](#pull-request)
+
+## Bug Report
+
+Did you find a bug? Be sure to set a clear and concise title. Do your best to
+include a code sample that illustrates the test case. Use the
+[template](ISSUE_TEMPLATE.md).
+
+## Pull Request
+
+Use the [template](PULL_REQUEST_TEMPLATE.md) and make sure:
+
+* **Required:** The build must pass. 
+* **Required:** Adherence to the  [Developer Certificate of Origin
+(DCO)](https://developercertificate.org/) version 1.1 (`git --signoff`).
+* **Required:** *squash your commits*. Yes, we know - it's nice to be able to
+rollback every single change you make while troubleshooting or when requested to
+exclude a subset or your change. The problem is the project's history tends to
+become polluted with useless commit messages such as "removed trailing spaces".
+It also makes it harder to revert specific changes when they are spread out like
+this. We care about preserving our project's commit history in a usable state,
+and as such, we politely request that you deliver your changes in a single
+commit.
+* Number of lines changed should not exceed 500. We're reasonable people - if
+your PR is just a *little* over the top then we might still merge it. Such cases
+are exceptional and are handled on a case-by-case basis.
+
+The contents of this file are heavily "borrowed" from  aries-framework-go, mainly because it is are good.

.github/ISSUE_TEMPLATE.md

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+Use the following template for your bug report
+(make sure you follow our [guidelines](CONTRIBUTING.md#bug-report):
+
+**What I'm trying to do**
+
+[Clearly describe what you're trying to do.]
+
+**Expected result**
+
+[Clearly describe the result you **expect**.]
+
+**Actual result**
+
+[Clearly describe the **actual** result you get.]
+
+**Sample code / test case**
+
+[Include a code sample that illustrates the test case.]

.github/PULL_REQUEST_TEMPLATE.md

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+Use the following template for your PR (make sure you follow our
+[guidelines](CONTRIBUTING.md#pull-request):
+
+**Title:**
+[Descriptive but using as few words as possible]
+
+**Description:**
+[Link to the GitHub issue it solves (if any)]
+
+Summary:
+
+[Include a brief summary of your changes]

.gitignore

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+build
+.idea/
+coverage.txt
+*.out

Makefile

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+.PHONY= all
+
+all: unit-test cover
+
+unit-test:
+	@scripts/test.sh
+
+cover:
+	go test -coverprofile cover.out ./pkg/...
+	go tool cover -html=cover.out

README.md

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+[![Release](https://img.shields.io/github/release/hyperledger/ursa-wrapper-go.svg?style=flat-square)](https://github.com/hyperledger/ursa-wrapper-go/releases/latest)
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://raw.githubusercontent.com/hyperledger/ursa-wrapper-go/main/LICENSE)
+[![Godocs](https://img.shields.io/badge/godoc-reference-blue.svg)](https://pkg.go.dev/github.com/hyperledger/ursa-wrapper-go)
+
+[![codecov](https://codecov.io/gh/hyperledger/ursa-wrapper-go/branch/main/graph/badge.svg?token=dXh8Imy2PO)](https://codecov.io/gh/hyperledger/ursa-wrapper-go)
+[![Go Report Card](https://goreportcard.com/badge/github.com/hyperledger/ursa-wrapper-go)](https://goreportcard.com/report/github.com/hyperledger/ursa-wrapper-go)
+
+## ursa-wrapper-go 
+
+- Ursa Wrapper Go requires the [Ursa](https://github.com/hyperledger/ursa) shared library to be installed (eg: /usr/local/lib), and `ursa-wrapper-go.sh` to be sourced. 
+
+```shell script
+source ursa-wrapper-go.sh
+```
+
+#### Development
+- `make test` to run unit tests 
+
+#### Requirements
+- Golang >= `1.14.4` and CGO enabled.

go.mod

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+module github.com/hyperledger/ursa-wrapper-go
+
+go 1.14

include/ursa_cl.h

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+#include <stdint.h>
+
+typedef enum {
+    Success = 0,
+    CommonInvalidParam1 = 100,
+    CommonInvalidParam2 = 101,
+    CommonInvalidParam3 = 102,
+    CommonInvalidParam4 = 103,
+    CommonInvalidParam5 = 104,
+    CommonInvalidParam6 = 105,
+    CommonInvalidParam7 = 106,
+    CommonInvalidParam8 = 107,
+    CommonInvalidParam9 = 108,
+    CommonInvalidParam10 = 109,
+    CommonInvalidParam11 = 110,
+    CommonInvalidParam12 = 111,
+    CommonInvalidState = 112,
+    CommonInvalidStructure = 113,
+    CommonIOError = 114,
+    AnoncredsRevocationAccumulatorIsFull = 115,
+    AnoncredsInvalidRevocationAccumulatorIndex = 116,
+    AnoncredsCredentialRevoked = 117,
+    AnoncredsProofRejected = 118,
+} ursa_error_t;
+
+struct ExternError {
+    ursa_error_t code;
+    char* message; /* note: nullable */
+};
+
+struct ExternError ursa_cl_new_nonce(void** nonce_p);
+struct ExternError ursa_cl_nonce_to_json(void* nonce, const char** nonce_json_p);
+extern void ursa_get_current_error(const char** error_json_p);

pkg/libursa/ursa/ursa.go

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+package ursa
+
+/*
+   #cgo LDFLAGS: -lursa
+   #include "ursa_cl.h"
+   #include <stdlib.h>
+*/
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+func NewNonce() (string, error) {
+	var nonce unsafe.Pointer
+	defer C.free(nonce)
+
+	var d *C.char
+	defer C.free(unsafe.Pointer(d))
+
+	result := C.ursa_cl_new_nonce(&nonce)
+	if result.code != 0 {
+		C.ursa_get_current_error(&result.message)
+		return "", errors.New(C.GoString(result.message))
+	}
+
+	result = C.ursa_cl_nonce_to_json(nonce, &d)
+	if result.code != 0 {
+		return "", errors.New(C.GoString(result.message))
+	}
+
+	return C.GoString(d), nil
+}

pkg/libursa/ursa/ursa_test.go

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+package ursa
+
+import (
+	"testing"
+)
+
+func TestNewNonce(t *testing.T) {
+	t.Run("NewNonce", func(t *testing.T) {
+		n, err := NewNonce()
+		if n == "" {
+			t.Errorf("NewNonce() returned blank value")
+		}
+
+		if err != nil {
+			t.Errorf("NewNonce() returned error")
+		}
+	})
+}

scripts/test.sh

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+#!/usr/bin/env bash
+
+set -e
+echo "" >coverage.txt
+
+for d in $(go list ./pkg/... | grep -v vendor); do
+  go test -race -coverprofile=profile.out -covermode=atomic $d
+  if [ -f profile.out ]; then
+    cat profile.out >>coverage.txt
+    rm profile.out
+  fi
+done

ursa-wrapper-go.sh

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+#!/bin/bash
+
+PWD=$(pwd)
+export URSA_GO_ROOT=$PWD
+export PATH=$PWD/bin:$PATH
+
+export CGO_CFLAGS=-I"${URSA_GO_ROOT}"/include