Drop support for Dart 2.6

.cider.yaml

@@ -0,0 +1,2 @@
+changelog:
+  diff_link_template: 'https://github.com/f3ath/json-api-dart/compare/%from%...%to%'

.travis.yml

@@ -2,7 +2,7 @@ language: dart
 dart:
   - stable
   - dev
-  - "2.6.0"
+  - "2.7.0"
 dart_task:
   - test: --platform vm
   - test: --platform chrome

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Removed
+- Dropped support for Dart 2.6
 
 ## [4.2.2] - 2020-06-05
 ### Fixed
@@ -69,7 +71,6 @@ is missing. Before in such cases a `FormatException` would be thrown ([pr](https
 - `IdentifierObject.fromIdentifier` factory method
 
 ### Changed
-Most of the changes are **BC-BREAKING**.
 - `URLBuilder` was renamed to `UrlFactory`.
 - `DocumentBuilder` was split into `ServerDocumentFactory` and `ClientDocumentFactory`. Some methods were renamed.
 - Static `decodeJson` methods were renamed to `fromJson`.
@@ -79,7 +80,7 @@ Most of the changes are **BC-BREAKING**.
 - The signature of `Controller`.
 - `Server` was renamed to `JsonApiServer`.
 - `Pagination` was renamed to `PaginationStrategy`.
- 
+
 ### Removed
 - (Server) `ResourceTarget`, `CollectionTarget`, `RelationshipTarget`  classes.
 - `QueryParameters` interface.
@@ -103,22 +104,20 @@ Most of the changes are **BC-BREAKING**.
 - Readme example was outdated.
 
 ## [2.0.0] - 2019-07-12
-
 ### Changed
 - This package now consolidates the Client, the Server and the Document in one single library. 
-    It does not depend on `json_api_document` and `json_api_server` anymore, please remove these packages 
-    from your `pubspec.yaml`.
+  It does not depend on `json_api_document` and `json_api_server` anymore, please remove these packages 
+  from your `pubspec.yaml`.
 - The min Dart SDK version bumped to `2.3.0`
 - The Client requires an instance of HttpClient to be passed to the constructor explicitly.
 - Both the Document and the Server have been refactored with lots of **BREAKING CHANGES**. 
-    See the examples and the functional tests for details.
+  See the examples and the functional tests for details.
 - Meta properties are not defensively copied, but set directly. Meta property behavior is unified across 
-    the Document model.
+  the Document model.
 
 ### Removed
 - `JsonApiParser` is removed. Use the static `decodeJson` methods in the corresponding classes instead.
 
-
 ## [1.0.1] - 2019-04-05
 ### Fixed
 - Bumped the dependencies versions due to a bug in `json_api_document`.
@@ -133,36 +132,36 @@ Most of the changes are **BC-BREAKING**.
 - Renamed `client.removeToOne(...)` to `client.deleteToOne(...)`
 
 ## [0.5.0] - 2019-03-21
+### Added
+- Related collection pagination
+- Async operations support
+
 ### Changed
 - More BC-breaking changes in the Server
 
 ### Fixed
 - Location headers generated incorrectly
 
+## [0.4.0] - 2019-03-17
 ### Added
-- Related collection pagination
-- Async operations support
+- Compound documents support in Client (Server-side support is still very limited)
 
-## [0.4.0] - 2019-03-17
 ### Changed
 - Parsing logic moved out
 - Some other BC-breaking changes in the Document
 - Huge changes in the Server
 
-### Added
-- Compound documents support in Client (Server-side support is still very limited)
-
 ### Fixed
 - Server was not setting links for resources and relationships
 
 ## [0.3.0] - 2019-03-16
-### Changed
-- Huge BC-breaking refactoring in the Document model which propagated everywhere
-
 ### Added
 - Resource attributes update
 - Resource relationships update
 
+### Changed
+- Huge BC-breaking refactoring in the Document model which propagated everywhere
+
 ## [0.2.0] - 2019-03-01
 ### Added
 - Improved ResourceController error handling
@@ -195,4 +194,4 @@ Most of the changes are **BC-BREAKING**.
 [0.5.0]: https://github.com/f3ath/json-api-dart/compare/0.4.0...0.5.0
 [0.4.0]: https://github.com/f3ath/json-api-dart/compare/0.3.0...0.4.0
 [0.3.0]: https://github.com/f3ath/json-api-dart/compare/0.2.0...0.3.0
-[0.2.0]: https://github.com/f3ath/json-api-dart/compare/0.1.0...0.2.0
+[0.2.0]: https://github.com/f3ath/json-api-dart/compare/0.1.0...0.2.0

pubspec.yaml

@@ -3,7 +3,7 @@ version: 4.2.2
 homepage: https://github.com/f3ath/json-api-dart
 description: Framework-agnostic implementations of JSON:API Client (Flutter, Web and VM) and Server (VM). Supports JSON:API v1.0 (http://jsonapi.org)
 environment:
-  sdk: '>=2.6.0 <3.0.0'
+  sdk: '>=2.7.0 <3.0.0'
 dependencies:
   http: ^0.12.0
   http_parser: ^3.1.4