Build Dataframe of Metadata from {xportr} attributes

[mstackhouse]

• Read a dataframe (we can do this using read_dataset_json()
• Add a new variable to it
• Apply the attributes using the xportr functions xportr_length() and xportr_label(). Type should be inferred from the variable (for now assume integer and string for simplicity of POC).
• With the attributes applied, construct the following dataframe:

                OID             name                                label    type length
1  ITEMGROUPDATASEQ ITEMGROUPDATASEQ                    Record Identifier integer     NA
2     IT.DM.STUDYID          STUDYID                     Study Identifier  string     12
3      IT.DM.DOMAIN           DOMAIN                  Domain Abbreviation  string      2
4     IT.DM.USUBJID          USUBJID            Unique Subject Identifier  string      8
5      IT.DM.SUBJID           SUBJID     Subject Identifier for the Study  string      4
6     IT.DM.RFSTDTC          RFSTDTC    Subject Reference Start Date/Time  string     NA
7     IT.DM.RFENDTC          RFENDTC      Subject Reference End Date/Time  string     NA
8    IT.DM.RFXSTDTC         RFXSTDTC   Date/Time of First Study Treatment  string     NA
9    IT.DM.RFXENDTC         RFXENDTC    Date/Time of Last Study Treatment  string     NA
10    IT.DM.RFICDTC          RFICDTC        Date/Time of Informed Consent  string     NA
11   IT.DM.RFPENDTC         RFPENDTC    Date/Time of End of Participation  string     NA
12     IT.DM.DTHDTC           DTHDTC                   Date/Time of Death  string     NA
13      IT.DM.DTHFL            DTHFL                   Subject Death Flag  string      1
14     IT.DM.SITEID           SITEID                Study Site Identifier  string      3
15    IT.DM.BRTHDTC          BRTHDTC                   Date/Time of Birth  string     NA
16        IT.DM.AGE              AGE                                  Age integer      8
17       IT.DM.AGEU             AGEU                            Age Units  string      5
18        IT.DM.SEX              SEX                                  Sex  string      1
19       IT.DM.RACE             RACE                                 Race  string     41
20     IT.DM.ETHNIC           ETHNIC                            Ethnicity  string     22
21      IT.DM.ARMCD            ARMCD                     Planned Arm Code  string      8
22        IT.DM.ARM              ARM           Description of Planned Arm  string     28
23   IT.DM.ACTARMCD         ACTARMCD                      Actual Arm Code  string      8
24     IT.DM.ACTARM           ACTARM            Description of Actual Arm  string     28
25     IT.DM.ARMNRS           ARMNRS Reason Arm and/or Actual Arm is Null  string     14
26   IT.DM.ACTARMUD         ACTARMUD  Description of Unplanned Actual Arm  string    200
27    IT.DM.COUNTRY          COUNTRY                              Country  string      3

In the OID column, the DM portion should be inferred from the object name of the variable passed into the function.