Initialize draft specification for error object format

text/0061-error-format.md

@@ -0,0 +1,49 @@
+- Title: Error Format
+- Start Date: 2021-08-13
+- Specification PR: [#61](https://github.com/meilisearch/specifications/pull/61)
+- Discovery Issue: [#44](https://github.com/meilisearch/product/issues/44#issuecomment-896121211)
+
+# Error Format
+
+## 1. Functional Specification
+
+### I. Summary
+
+The error format is updated to no longer contain unnecessary `error` prefix terms in the names of these attributes. The context is clear enough to understand that this is an `error` object.
+
+#### Summary Key Points
+
+- `error` is removed from attributes name.
+
+### II. Motivation
+
+The main motivation is to stabilize the current `error` resource to a version that conforms to our API convention and thus allow future evolutions on a more solid base. This specification avoids adding unnecessary information in the object's attribute names.
+
+### III. Explanation
+
+#### Error Format Definition
+
+| Field name | type   | Description                                                              |
+|------------|--------|--------------------------------------------------------------------------|
+| message    | string |  A human-readable message providing context and details about the error  |
+| code       | string |  An error code                                                           |
+| type       | string |  An error type for which the error code is linked                        |
+| link       | string |  An URL to the related error-page details                                |
+
+e.g. 401 Unauthorized Response example
+
+```
+{
+    "message": "authorization header is missing",
+    "code": "missing_authorization_header",
+    "type": "authentication_error",
+    "link": "https://docs.meilisearch.com/errors#missing_authorization_header"
+}
+```
+
+## 2. Technical details
+N/A
+
+## 3. Future Possibilities
+
+- Add a `parameter` attribute in the `error` object to indicate which parameter of the request caused an error.