Add additional validation to swarming v1 distributor.

dm/api/distributor/swarming/v1/params.pb.go

 // Code generated by protoc-gen-go.
 // source: github.com/luci/luci-go/dm/api/distributor/swarming/v1/params.proto
 // DO NOT EDIT!
 
 package swarmingV1
 
 import proto "github.com/golang/protobuf/proto"
 import fmt "fmt"
 import math "math"
 import google_protobuf "github.com/luci/luci-go/common/proto/google"
@@ skipping 139 matching lines @@
 type Parameters_Job_Inputs struct {
         // 0 or more isolated IDs that will be 'included' together into the final
         // job .isolated sent to swarming.
         //
         // The "server" value must either be omitted, or equal the isolate server
         // defined by this distributor's config (the `isolate.host` field,
         // prepended with "https://").
         Isolated []*IsolatedRef `protobuf:"bytes,1,rep,name=isolated" json:"isolated,omitempty"`
         // 0 or more cipd packages for the job.
         Packages []*Parameters_Job_Inputs_CipdPackage `protobuf:"bytes,2,rep,name=packages" json:"packages,omitempty"`
-        // Optional server to use for cipd packages. If you know you're using
-        // swarming's default server, you can omit this.
+        // Server to use for cipd packages. Required (though it may be specified
+        // by the quest's designated distributor config). This must be
+        // scheme://<hostname>, e.g. "https://example.appspot.com". The only
+        // supported schemes are http and https.
         CipdServer string `protobuf:"bytes,3,opt,name=cipd_server,json=cipdServer" json:"cipd_server,omitempty"`
 }
 
 func (m *Parameters_Job_Inputs) Reset()                    { *m = Parameters_Job_Inputs{} }
 func (m *Parameters_Job_Inputs) String() string            { return proto.CompactTextString(m) }
 func (*Parameters_Job_Inputs) ProtoMessage()               {}
 func (*Parameters_Job_Inputs) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{0, 2, 0} }
 
 func (m *Parameters_Job_Inputs) GetIsolated() []*IsolatedRef {
         if m != nil {
@@ skipping 65 matching lines @@
         0x43, 0x94, 0x8f, 0xff, 0xa1, 0x78, 0x9a, 0xaf, 0xab, 0xf0, 0x3c, 0x1e, 0xff, 0xee, 0x40, 0xaf,
         0xba, 0x03, 0x1d, 0x42, 0xbf, 0x7e, 0x84, 0x89, 0x33, 0xe6, 0x65, 0x6e, 0x6f, 0xcb, 0x4c, 0xea,
         0x33, 0x26, 0x16, 0xac, 0x05, 0xa2, 0x89, 0x2b, 0x99, 0xcf, 0xcf, 0x79, 0x2a, 0x9a, 0x1a, 0x0f,
         0x76, 0xfe, 0x0d, 0x39, 0x96, 0x45, 0x32, 0xad, 0x58, 0xac, 0xa5, 0xfb, 0xfc, 0xe6, 0xee, 0x60,
         0x66, 0x84, 0x5e, 0x0b, 0x1d, 0x1a, 0x74, 0xf9, 0xf9, 0xd1, 0x59, 0x98, 0xe0, 0x8f, 0x30, 0xdc,
         0x62, 0x22, 0x04, 0x5d, 0x1f, 0x6e, 0x1d, 0x74, 0x58, 0xfb, 0x59, 0xc1, 0xed, 0xb2, 0x2e, 0x29,
         0xac, 0x7d, 0x66, 0x8e, 0xed, 0xcb, 0xad, 0x35, 0x9b, 0x2d, 0x7e, 0x09, 0xfd, 0x26, 0x8d, 0xff,
         0x69, 0x3c, 0xee, 0x85, 0xe7, 0x74, 0xf8, 0x27, 0x00, 0x00, 0xff, 0xff, 0x7f, 0xfc, 0xb8, 0xa6,
         0x5d, 0x04, 0x00, 0x00,
 }