Compliance-checker

Release for the IOOS Metadata Profile Version 1.2 Checker.

General
- Enables fetching from remote, non-OPeNDAP NetCDF files which use a `Content-Type` header of `application/x-netcdf`
- Enables fetching of datasets from ERDDAP TableDAP endpoints
- Skips iterating Python setup requirements twice
- Escape variable output in HTML format
- Allow in-memory loading of remote NetCDF datasets

CI/Build
- Adds pre-commit hooks in GitHub

IOOS Checker
- Update GTS ingest logic
- Correct platform detection
- Add z variable logic
- Various fixes/improvements to error messages

Release candidate 2 for the IOOS Metadata Profile Version 1.2 Checker

- change `standard_name_uri` to `standard_name_url`
- add syntax checks for `platform_id`
- add checks for `flag_meanings` and `flag_values` on QARTOD variables
- streamline messaging for `ioos_ingest`, `gts_ingest` checks
- ensure proper syntax for `wmo_platform_code`
- separate checks for global `gts_ingest` flag and checking if the variables passed the GTS ingest requirements
- improve messaging for `qartod_variables:references` check
- add documentation for using ERDDAP datasets with the checker

Release Candidate version 1 for IOOS Compliance Checker 4.3.3.

General
- Adds a `ValidationObject` class in `base.py` for generic validation of global attributes. Current uses include email and URL validation, among others.
- Updates `attr_check` function to accept variables for generic variable checks, e.g. aforementioned validators, set membership from known set of strings.

General:
- Adds a new `--option`/`-O` command line flag which can be used to alter desired checker behavior. This option can be specified multiple times for several options, although as of this release, there is only one supported option (see notes in CF section below).

Changes to CF checkers (all versions):
- Corrects "coordinate data variable" finding routines to correspond with CF Section 1.3 "Overview". Coordinate data variables now find both NUG "coordinate variables", which are variables with one dimension where the dimension has the same name as the variable, and variables referred to by the contents of the `coordinates` attribute in other variables.
- Improves readability of error message for attributes which are improperly placed according to CF Appendix A's "Use" column.
- Disables checking of Appendix A by default and only checks Appendix A if `cf:enable_appendix_a_checks` is specified in aforementioned `-O`/`--option` flags via the CLI.

Compliance Checker 4.3.0: CF 1.7 Release
========================================

The latest major release for the IOOS Compliance Checker contains updated checks
to reflect CF-1.7, the most current stable CF Conventions document at the time of this release. The software includes
numerous changes, most notably:

1. Dropped support for Python 2.7
2. Updated list of Grid Mapping attributes in [Table F1](http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/cf-conventions.html#table-grid-mapping-attributes)
and checks for Well-Known Text (WKT) strings using the PROJ database
3. Added new projections
4. Check against computed_standard_name attribute
5. Check against [Appendix A](http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/cf-conventions.html#attribute-appendix) attributes

For a comprehensive list of the issues addressed and changes made, see the [milestone](https://github.com/ioos/compliance-checker/milestone/10?closed=1).

Patch release containing:

- links to new IOOS Metadata Profile repo
- an update to setup.py
- a bug fix on the html reports