…ce, but do write them when logging

…ead it (false by default)

…n request body (false by default)

The existing validation logic inside controllers, JsonApiReader and RequestDeserializer/BaseDeserializer has been consolidated into a set of adapters that delegate to each other, passing along the current state. The dependency on `HttpContext` has been removed and similar errors are now grouped, in preparation to unify them. Because in this commit we always track the location of errors and write them to `error.source.pointer`, the error messages can be unified and simplified in future commits.

In this commit, I've gone through great lenghts to preserve the existing error messages in our tests as much as possible, while keeping all tests green. All error tests in ReadWrite and Operations now have assertions on the source pointer. Added tests for missing/invalid 'data' in resource requests. Removed outdated unit tests and added new one for handling attributes of various CLR types.

Updated benchmark code. The synthetic BenchmarkDotNet reports it has become 3-7% slower (we're talking microseconds here) compared to the old code. But when running full requests with our pipeline-instrumentation turned on, the difference falls in the range of background noise and is thus unmeasurable.

```
BEFORE:
          Read request body ...............................  0:00:00:00.0000167 ...   1.08%  } 167 + 434 = 601
            JsonSerializer.Deserialize ....................  0:00:00:00.0000560 ...   3.62%  +
            Deserializer.Build (single) ...................  0:00:00:00.0000434 ...   2.80%  }

AFTER:
          Read request body ...............................  0:00:00:00.0000511 ...   3.43%
            JsonSerializer.Deserialize ....................  0:00:00:00.0000537 ...   3.61%
```

…ody does not get added to the error response meta

…/array

- IOperationsDocumentAdapter -> IDocumentInOperationsRequestAdapter
- IResourceDocumentAdapter -> IDocumentInResourceOrRelationshipRequestAdapter
- IOperationResourceDataAdapter -> IResourceDataInOperationsRequestAdapter

- Changed deserializer to accept Error(s) instead of Document (used to be ErrorDocument, but they were merged)
- Write request body in error meta instead of top-level meta
- Fixed: Log at Error instead of Info when processing an operation throws unknown error

…ains mixed types

…teOperation is now populated consistently; applied c# pattern usage

…id operations. The spec allows an empty object too, but I don't consider this important enough to add yet another JSON converter with all its overhead.

- Added temporary bridge class to toggle between old/new code
- Fixed: Missing top-level link in error- and operations response
- Fixed: `ILinkBuilder.GetResourceLinks` was also used to render relationship links
- IJsonApiRequest management: restore backup after processing operations
- Refreshed serialization benchmarks

Measurement results for GET http://localhost:14140/api/v1/todoItems?include=owner,assignee,tags:
    Write response body ............................  0:00:00:00.0010385 ->  0:00:00:00.0013343 = 130%

Measurement results for GET http://localhost:14140/api/v1/todoItems?filter=and(startsWith(description,'T'),equals(priority,'Low'),not(equals(owner,null)),not(equals(assignee,null))):
    Write response body ............................  0:00:00:00.0006601 -> 0:00:00:00.0004624 = 70%

Measurement results for POST http://localhost:14140/api/v1/operations (10x add-resource):
    Write response body ............................  0:00:00:00.0003432 -> 0:00:00:00.0003289 = 95%

|                            Method |     Mean |   Error |  StdDev |
|---------------------------------- |---------:|--------:|--------:|
|       SerializeOperationsResponse | 153.8 us | 0.72 us | 0.60 us |
| LegacySerializeOperationsResponse | 239.0 us | 3.17 us | 2.81 us |

|                          Method |     Mean |   Error |  StdDev |
|-------------------------------- |---------:|--------:|--------:|
|       SerializeResourceResponse | 101.3 us | 0.31 us | 0.29 us |
| LegacySerializeResourceResponse | 177.6 us | 0.56 us | 0.50 us |

https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/HEAD

… when empty

…onship left/right. This enabled to reduce many resource graph lookups from the codebase.

…Builder for easier reuse.

It now always emits related resources in relationship declaration order, even in deeply nested circular chains where a subsequent inclusion chain is deeper and adds more relationships to an already converted resource.

Performance impact, summary:
- In the endpoint test, this commit improves performance for rendering includes, while slightly decreasing it for the other two scenarios. All are still faster or the same compared to the master branch.
- In BenchmarkDotNet, this commit slightly increases rendering time, compared to earlier commits in this PR, but it is still faster than the master branch.

Measurement results for GET http://localhost:14140/api/v1/todoItems?include=owner,assignee,tags:
    Write response body .............................  0:00:00:00.0010385 -> 0:00:00:00.0008060 ...  77% (was: 130%)

Measurement results for GET http://localhost:14140/api/v1/todoItems?filter=and(startsWith(description,'T'),equals(priority,'Low'),not(equals(owner,null)),not(equals(assignee,null))):
    Write response body .............................  0:00:00:00.0006601 -> 0:00:00:00.0005629 ...  85% (was: 70%)

Measurement results for POST http://localhost:14140/api/v1/operations (10x add-resource):
    Write response body .............................  0:00:00:00.0003432 -> 0:00:00:00.0003411 ...  99% (was: 95%)

|                            Method |     Mean |   Error |  StdDev |
|---------------------------------- |---------:|--------:|--------:|
| LegacySerializeOperationsResponse | 239.0 us | 3.17 us | 2.81 us |
|       SerializeOperationsResponse | 153.8 us | 0.72 us | 0.60 us |
| (new) SerializeOperationsResponse | 168.6 us | 1.74 us | 1.63 us |

|                          Method |     Mean |   Error |  StdDev |
|-------------------------------- |---------:|--------:|--------:|
| LegacySerializeResourceResponse | 177.6 us | 0.56 us | 0.50 us |
|       SerializeResourceResponse | 101.3 us | 0.31 us | 0.29 us |
| (new) SerializeResourceResponse | 123.7 us | 1.12 us | 1.05 us |