Multipart Body parsing

[schloerke]

Fixes #662

• Rename many forms of postBody to body
• If a body is received by Plumber, store the parsed value in req$body
• If a multipart body is parsed, the values used in req$argsBody are the plucked parsed values of each part in req$body.
• parser_octet() only returns the raw value as is

PR task list:

• Update NEWS
• Add tests
• Update documentation with devtools::document()

Pseudo code structure information:

multipart/* POST:
- req$bodyRaw - raw vector
  - req$postbody (obsolete)
- req$argsBody - list(partname = data.frame(), partname2 = raw())
- req$args - will contain list(partname = data.frame(), partname2 = raw())
- req$body = list(partname = webutils_output(), partname2 = webutils_output())

Example req$argsBody

> str(req$body)
List of 5
 $ files:List of 6
  ..$ value              : raw [1:1117] 89 50 4e 47 ...
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "image/png"
  ..$ name               : chr "files"
  ..$ filename           : chr "avatar2-small.png"
  ..$ parsed             : raw [1:1117] 89 50 4e 47 ...
 $ files:List of 6
  ..$ value              : raw 61
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "application/octet-stream"
  ..$ name               : chr "files"
  ..$ filename           : chr "text1.bin"
  ..$ parsed             : raw 61
 $ files:List of 6
  ..$ value              : raw 62
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "application/octet-stream"
  ..$ name               : chr "files"
  ..$ filename           : chr "text2.bin"
  ..$ parsed             : raw 62
 $ files:List of 6
  ..$ value              : raw 63
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "application/octet-stream"
  ..$ name               : chr "files"
  ..$ filename           : chr "text3.bin"
  ..$ parsed             : raw 63
 $ dt   :List of 4
  ..$ value              : raw [1:2] 7b 7d
  ..$ content_disposition: chr "form-data"
  ..$ name               : chr "dt"
  ..$ parsed             : Named list()
 - attr(*, "class")= chr "plumber_multipart"

> str(req$argsBody)
List of 2
 $ files:List of 4
  ..$ avatar2-small.png: raw [1:1117] 89 50 4e 47 ...
  ..$ text1.bin        : raw 61
  ..$ text2.bin        : raw 62
  ..$ text3.bin        : raw 63
 $ dt   : Named list()

> str(req$body)
List of 4
 $ json:List of 4
  ..$ value              : raw [1:59] 7b 0a 20 20 ...
  ..$ content_disposition: chr "form-data"
  ..$ name               : chr "json"
  ..$ parsed             :List of 3
  .. ..$ a: int 2
  .. ..$ b: int 4
  .. ..$ c:List of 2
  .. .. ..$ w: int 3
  .. .. ..$ t: int 5
 $ img1:List of 6
  ..$ value              : raw [1:1117] 89 50 4e 47 ...
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "image/png"
  ..$ name               : chr "img1"
  ..$ filename           : chr "avatar2-small.png"
  ..$ parsed             : raw [1:1117] 89 50 4e 47 ...
 $ img2:List of 6
  ..$ value              : raw [1:1537] 89 50 4e 47 ...
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "image/png"
  ..$ name               : chr "img2"
  ..$ filename           : chr "ragnarok_small.png"
  ..$ parsed             : raw [1:1537] 89 50 4e 47 ...
 $ rds :List of 6
  ..$ value              : raw [1:211] 1f 8b 08 00 ...
  ..$ content_disposition: chr "form-data"
  ..$ content_type       : chr "application/rds"
  ..$ name               : chr "rds"
  ..$ filename           : chr "women.rds"
  ..$ parsed             :'data.frame':	15 obs. of  2 variables:
  .. ..$ height: num [1:15] 58 59 60 61 62 63 64 65 66 67 ...
  .. ..$ weight: num [1:15] 115 117 120 123 126 129 132 135 139 142 ...
 - attr(*, "class")= chr "plumber_multipart"

> str(req$argsBody)
List of 4
 $ json:List of 3
  ..$ a: int 2
  ..$ b: int 4
  ..$ c:List of 2
  .. ..$ w: int 3
  .. ..$ t: int 5
 $ img1:List of 1
  ..$ avatar2-small.png: raw [1:1117] 89 50 4e 47 ...
 $ img2:List of 1
  ..$ ragnarok_small.png: raw [1:1537] 89 50 4e 47 ...
 $ rds :List of 1
  ..$ women.rds:'data.frame':	15 obs. of  2 variables:
  .. ..$ height: num [1:15] 58 59 60 61 62 63 64 65 66 67 ...
  .. ..$ weight: num [1:15] 115 117 120 123 126 129 132 135 139 142 ...

cc @jcheng5