Add operator<<(json_pointer) (#3601)

* Add operator<< for json_pointer

* Deprecate json_pointer::operator string_t()

* Update documentation

* Move operator<<(basic_json) example

* Add example

* Add mkdocs-redirects

* Move operator<< and operator>> doc pages out of basic_json/

* Rename JSON pointer operator_string to operator_string_t

* Add unit test

docs/mkdocs/docs/api/basic_json/accept.md

@@ -96,7 +96,7 @@ Linear in the length of the input. The parser is a predictive LL(1) parser.
 ## See also
 
 - [parse](parse.md) - deserialize from a compatible input
-- [operator>>](operator_gtgt.md) - deserialize from stream
+- [operator>>](../operator_gtgt.md) - deserialize from stream
 
 ## Version history
 

docs/mkdocs/docs/api/basic_json/index.md

@@ -283,8 +283,8 @@ Access to the JSON value
 
 ## Non-member functions
 
-- [**operator<<(std::ostream&)**](operator_ltlt.md) - serialize to stream
-- [**operator>>(std::istream&)**](operator_gtgt.md) - deserialize from stream
+- [**operator<<(std::ostream&)**](../operator_ltlt.md) - serialize to stream
+- [**operator>>(std::istream&)**](../operator_gtgt.md) - deserialize from stream
 - [**to_string**](to_string.md) - user-defined `to_string` function for JSON values
 
 ## Literals

docs/mkdocs/docs/api/basic_json/operator_gtgt.md

@@ -1,65 +0,0 @@
-# operator>>(basic_json)
-
-```cpp
-std::istream& operator>>(std::istream& i, basic_json& j);
-```
-
-Deserializes an input stream to a JSON value.
-
-## Parameters
-
-`i` (in, out)
-:   input stream to read a serialized JSON value from
-
-`j` (in, out)
-:   JSON value to write the deserialized input to
-
-## Return value
-
-the stream `i`
-
-## Exceptions
-
-- Throws [`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101) in case of an unexpected token.
-- Throws [`parse_error.102`](../../home/exceptions.md#jsonexceptionparse_error102) if to_unicode fails or surrogate 
-  error.
-- Throws [`parse_error.103`](../../home/exceptions.md#jsonexceptionparse_error103) if to_unicode fails.
-
-## Complexity
-
-Linear in the length of the input. The parser is a predictive LL(1) parser.
-
-## Notes
-
-A UTF-8 byte order mark is silently ignored.
-
-## Examples
-
-??? example
-
-    The example below shows how a JSON value is constructed by reading a serialization from a stream.
-        
-    ```cpp
-    --8<-- "examples/operator_deserialize.cpp"
-    ```
-    
-    Output:
-    
-    ```json
-    --8<-- "examples/operator_deserialize.output"
-    ```
-
-## See also
-
-- [accept](accept.md) - check if the input is valid JSON
-- [parse](parse.md) - deserialize from a compatible input
-
-## Version history
-
-- Added in version 1.0.0
-
-!!! warning "Deprecation"
-
-    This function replaces function `#!cpp std::istream& operator<<(basic_json& j, std::istream& i)` which has
-    been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like `#!cpp j << i;`
-    with `#!cpp i >> j;`.

docs/mkdocs/docs/api/basic_json/operator_ltlt.md

@@ -1,62 +0,0 @@
-# operator<<(basic_json)
-
-```cpp
-std::ostream& operator<<(std::ostream& o, const basic_json& j);
-```
-
-Serialize the given JSON value `j` to the output stream `o`. The JSON value will be serialized using the
-[`dump`](dump.md) member function.
-
-- The indentation of the output can be controlled with the member variable `width` of the output stream `o`. For
-  instance, using the manipulator `std::setw(4)` on `o` sets the indentation level to `4` and the serialization result
-  is the same as calling `dump(4)`.
-- The indentation character can be controlled with the member variable `fill` of the output stream `o`. For instance,
-  the manipulator `std::setfill('\\t')` sets indentation to use a tab character rather than the default space character.
-
-## Parameters
-
-`o` (in, out)
-:   stream to serialize to
-
-`j` (in)
-:   JSON value to serialize
-
-## Return value
-
-the stream `o`
-
-## Exceptions
-
-Throws [`type_error.316`](../../home/exceptions.md#jsonexceptiontype_error316) if a string stored inside the JSON value
-is not UTF-8 encoded. Note that unlike the [`dump`](dump.md) member functions, no `error_handler` can be set.
-
-## Complexity
-
-Linear.
-
-## Examples
-
-??? example
-
-    The example below shows the serialization with different parameters to `width` to adjust the indentation level.
-        
-    ```cpp
-    --8<-- "examples/operator_serialize.cpp"
-    ```
-    
-    Output:
-    
-    ```json
-    --8<-- "examples/operator_serialize.output"
-    ```
-
-## Version history
-
-- Added in version 1.0.0
-- Support for indentation character added in version 3.0.0.
-
-!!! warning "Deprecation"
-
-    This function replaces function `#!cpp std::ostream& operator>>(const basic_json& j, std::ostream& o)` which has
-    been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like `#!cpp j >> o;`
-    with `#!cpp o << j;`.

docs/mkdocs/docs/api/basic_json/parse.md

@@ -196,7 +196,7 @@ super-linear complexity.
 ## See also
 
 - [accept](accept.md) - check if the input is valid JSON
-- [operator>>](operator_gtgt.md) - deserialize from stream
+- [operator>>](../operator_gtgt.md) - deserialize from stream
 
 ## Version history