Add specific warnings for B0Field*, deduplicate sidecar tables

Author: effigies

src/modality-specific-files/magnetic-resonance-imaging-data.md

@@ -161,7 +161,7 @@ A guide for using macros can be found at
  https://github.com/bids-standard/bids-specification/blob/master/macros_doc.md
 -->
 {{ MACROS___make_sidecar_table([
-     "mri.MRIB0FieldIdentifier",
+     "fmap.MRIFieldmapB0FieldIdentifier",
      "mri.MRIEchoPlanarImagingAndB0FieldSource",
    ])
 }}

src/schema/rules/sidecars/fmap.yaml

@@ -23,7 +23,16 @@ MRIFieldmapB0FieldIdentifier:
     - match(extension, '\.nii(\.gz)?$')
     - '!("IntendedFor" in sidecar)'
   fields:
-    B0FieldIdentifier: recommended
+    B0FieldIdentifier:
+      level: recommended
+      issue:
+        code: B0_FIELD_IDENTIFIER_RECOMMENDED
+        message: |
+          File is missing B0FieldIdentifier metadata and IntendedFor metadata,
+          so it will not be possible to use to perform susceptibility distortion correction.
+          B0FieldIdentifier metadata permits the flexible selection of images
+          for estimating B0 inhomogeneity fields, and B0FieldSource permits EPI
+          images to indicate the identifier of the estimated field to use.
 
 # Case 1: Phase-difference map and at least one magnitude image
 MRIFieldmapPhaseDifferencePhasediff:

src/schema/rules/sidecars/mri.yaml

@@ -385,7 +385,17 @@ MRIEchoPlanarImagingAndB0FieldSource:
     - intersects(dataset.datatypes, ['fmap'])
     - match(extension, "^\.nii(\.gz)?$")
   fields:
-    B0FieldSource: recommended
+    B0FieldSource:
+      level: recommended
+      issue:
+        code: B0_FIELD_SOURCE_RECOMMENDED
+        message: |
+          File is missing B0FieldSource metadata, so it may not be possible to
+          perform susceptibility distortion correction on it.
+          B0FieldIdentifier metadata permits the flexible selection of images
+          for estimating B0 inhomogeneity fields, and B0FieldSource permits EPI
+          images to indicate the identifier of the estimated field to use.
+          If associations are fully specified with `IntendedFor`, there is no need to change this.
 
 MRIInstitutionInformation:
   selectors: